Chemistry and the Chemical Industry a Practical Guide for Non-Chemists

CRC PR ESSBoca Raton London New York Washington, D.C.

A Practical Guidefor Non-Chemists

CHEMISTRY

and theCHEMICAL INDUSTRYRobert A. Smiley, Ph.D.Harold L. Jackson, Ph.D.

© 2002 by CRC Press LLC

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No claim to original U.S. Government worksInternational Standard Book Number 1-58716-054-4

Library of Congress Card Number 2001052817Printed in the United States of America 1 2 3 4 5 6 7 8 9 0

Printed on acid-free paper

Library of Congress Cataloging-in-Publication Data

Smiley, Robert A.Chemistry and the chemical industry : a practical guide for non-chemists / Robert A.

Smiley, Harold L. Jackson.p. cm.

Includes bibliographical references and index.ISBN 1-58716-054-4 (alk. paper)1. Chemistry, Technical. I. Jackson, Harold L. (Harold Leonard), 1923- II. Title.

TP145 .S65 2002660—dc21 2001052817

CIP

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Preface

The chemical industry affects virtually all aspects of our lives. Were it todisappear suddenly, we would find ourselves living again in the early nine-teenth century without cars, airplanes, television, electric lights, most of ourcolorful clothing, most perishable food, most drugs and medicine, plastics,and all the rest of the modern conveniences that most of us take for granted.

Consider how the chemical industry contributes to your daily life. Forexample, when you get up in the morning, you brush your teeth usingtoothpaste, which is a mixture of chemicals squeezed from a plastic tubeonto plastic bristles mounted in a plastic handle. You may take a showerusing soap and shampoo, each made by the chemical industry, and finallydry, brush, or comb your hair with other articles made of plastic. While doingthis, you will likely be looking into a mirror over a porcelain or culturedmarble sink while standing on vinyl plastic floorcovering, tile, or carpeting,all of which are products of the chemical industry. The varnish coating thewooden floors of your house and the paint or wallpaper covering the wallsare products of the chemical industry. At breakfast, it is likely that the kitchencounters and table are topped with plastic, as are the chairs. The refrigeratorwould not work without chemicals either for the refrigeration unit or theinsulation in its walls. The interior is plastic lined and the exterior has adurable coating made possible by the chemical industry. Your breakfast foodis probably fresh because it was treated with chemical preservatives and/orshipped in a box with a plastic lining. The car or bus that you go to workin is totally chemical dependent, from the anti-corrosion treatment of themetal, the protective paint and the plastic parts and tires to the chemicalbattery that starts the vehicle, the oil that lubricates it, and the gasoline thatfuels it. And so it goes.

The fact that our daily lives are so dependent on the chemical industrydoes not appear to be widely recognized, even by those working in thechemical industry. And so, as companies are forced in a world economy tobecome more productive and more quality conscious, as well as having agreater concern for the environment, it becomes essential that their presentand future employees understand the basic concepts upon which the chemicalindustry (indeed, our modern existence) is based. This book is designed toaid in that understanding by reviewing the important aspects of industrialchemistry in a way that can be understood even by those who have not takenany formal chemistry courses.

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No mathematics is used and basic physical science is minimized. Whychemicals behave as they do is not explained. It is assumed that the endresult of the manufacturing processes presented is the information wantedby the reader and not the science or engineering involved. If needed, thelatter information can be obtained from listed sources.

The first chapter begins with a description of the chemical industry andits unique features and branches. The most common terms used in chemistryare defined, using nonscientific analogies where possible. In the followingchapters, some basic organic chemistry is presented so that later descriptiveexplanations of the largest and most important products of the chemicalindustry can be better understood. The product descriptions include the rawmaterial sources, manufacturing processes, and, of most importance, theircommercial uses. Finally, there is a short compilation of general informationsources.

The style of the book is to present only a small amount of informationon each page with a slide-like illustration using short descriptions and easilyunderstood chemical equations and structures. Under each illustration isadditional information or comments with room for the reader to make notesif desired. Although there is obvious continuity, an attempt has been madeto make each page subject somewhat independent so that readers can studythe contents of the book one page at a time at their own pace. Of necessity,because of this format, there is considerable repetition. We do not considerthis bad.

Robert A. SmileyHarold L. Jackson

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Authors

Robert A. Smiley, Ph.D.

retired from the DuPont Company in 1990, after whichhe became an independent consultant in general industrial chemistry. Clients haveincluded ICI, Westinghouse, Clorox, Arco, and many smaller chemical companies.Currently he consults for Dixie Chemical Company where he holds the title ofcorporate research fellow. He is also the president of Falcon Lab LLC, a companyengaged in patent licensing. His fields of expertise include nitrile chemistry, diiso-cyanate and polyurethane chemistry, nitric acid oxidation, and nitration chemistryand explosives. For many years he gave sponsored seminars on industrial chemistryand polyurethane chemistry both in Europe and the U.S. He received a B.S. degreein industrial chemistry from Case Institute of Technology and a Ph.D. in organicchemistry from Purdue University and joined DuPont as a research chemist in 1954.After a number of successful assignments in the process development of polymerintermediates, he became a research supervisor and then moved on to other positionsin technology licensing, business analysis and back to research as research associateand research fellow. He holds 26 U.S. patents and is the author or co-author of 13publications.

Harold L. Jackson, Ph.D.

has 51 years of experience in the chemical industry. Afterreceiving a Ph.D. in organic chemistry from the University of Illinois in 1949, hejoined DuPont’s central research department where he made significant contributionsin the areas of inorganic, organic, and polymer chemistry. He later moved to otherresearch responsibilities in DuPont’s chemicals and petrochemicals departmentswhere he studied polymer synthesis and characterization, polymer intermediatedevelopment, and solvent chemistry. He has been involved in and assisted withmarketing efforts on commercial products resulting from his research work. Heretired in 1992 as a research fellow. Dr. Jackson holds 32 U.S. patents and is theauthor of numerous technical articles. In addition to his industrial activities, Dr.Jackson served as visiting professor of organic chemistry at the University of Kansas.

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Contents

Preface

......................................................................................................................iii

Chapter 1. Introduction

..........................................................................................1Chemical and Allied Products Industries..................................................................2Chemical Industry......................................................................................................3

Characteristics ..................................................................................................3The Beginnings ................................................................................................4Research and Development/Engineering Technology.....................................5History..............................................................................................................6

Language of Chemistry .............................................................................................7Chemistry...................................................................................................................8

Properties and Changes....................................................................................8Substance States...............................................................................................9Chemical Substances......................................................................................10Chemical Representation ...............................................................................11Symbols of Common Elements .....................................................................12Divisions.........................................................................................................13General Definitions ........................................................................................14

Chapter 2. Important Inorganic Chemicals

.......................................................151999 U.S. Annual Production..................................................................................16Sulfuric Acid (H

2

SO

4

) .............................................................................................17Nitrogen (N

2

) ...........................................................................................................19Inorganic Nitrogen Compounds ..............................................................................20Oxygen (O

2

).............................................................................................................21Lime (CaO)..............................................................................................................23Ammonia (NH

3

).......................................................................................................24Phosphoric Acid (H

3

PO

4

) ........................................................................................25Chlorine (Cl

2

)...........................................................................................................26Sodium Hydroxide (NaOH) ....................................................................................28Sodium Carbonate (Na

2

CO

3

)...................................................................................30Nitric Acid (HNO

3

)..................................................................................................32Hydrogen (H

2

) .........................................................................................................34

Chapter 3. Organic Chemistry

.............................................................................35Organic Chemistry...................................................................................................36Organic Compounds ................................................................................................37Carbon Structure......................................................................................................38

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Carbon Chains .........................................................................................................39Carbon–Carbon Multiple Bonds .............................................................................40Aliphatic Hydrocarbons...........................................................................................41

Paraffins..........................................................................................................41Structure .........................................................................................................42Structure: Long Hydrocarbon Chains............................................................43

Isomers.....................................................................................................................44Paraffin Names.........................................................................................................46Paraffins ...................................................................................................................48Functional Groups ...................................................................................................49Formulae ..................................................................................................................50Paraffins: Chemical Properties ................................................................................51

Types of Carbon Atoms .................................................................................51Chlorination....................................................................................................52Nitration .........................................................................................................53Oxidation........................................................................................................53Pyrolysis or “Cracking” .................................................................................53Isomerization..................................................................................................53

Unsaturated Hydrocarbons ......................................................................................54Olefins ............................................................................................................55

Olefins: Chemical Properties...................................................................................56Unsaturated Hydrocarbons ......................................................................................57

Acetylenes ......................................................................................................57Oxygenated Organic Compounds............................................................................58Oxidation..................................................................................................................59Alcohols ...................................................................................................................60Polyalcohols.............................................................................................................61Manufacture of Alcohols .........................................................................................62Aldehydes ................................................................................................................63Ketones ....................................................................................................................64Acids ........................................................................................................................65Esters........................................................................................................................67Ethers .......................................................................................................................69Nitrogen-Based Organic Compounds......................................................................70Amines .....................................................................................................................71Amides .....................................................................................................................72

Chapter 4. Aromatic Organic Chemistry

...........................................................73Aromatic Organic Chemistry ..................................................................................74

Benzene ..........................................................................................................74Substituted Benzenes .....................................................................................76Polyaromatic Compounds ..............................................................................84Carboxylic Acids............................................................................................85Phenols ...........................................................................................................87Amines ...........................................................................................................89

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Benzene-Based Intermediates for Epoxy Resins and Polycarbonates..........90Benzene-Based Intermediates to Polyurethanes............................................91

Chapter 5. Polymer Chemistry

............................................................................93Polymers ..................................................................................................................94Natural Polymers .....................................................................................................95Polymer Structure ....................................................................................................96Polymer Crystallinity...............................................................................................98Polymer Classes.......................................................................................................99Polymer Synthesis .................................................................................................100Step Growth Polymerization .................................................................................101

Examples ......................................................................................................102Chain Growth (Addition) Polymerization.............................................................105Typical Chain Growth Polymers ...........................................................................108Copolymers ............................................................................................................109Polyethylene...........................................................................................................110Polypropylene ........................................................................................................111Poly(vinyl chloride) ...............................................................................................112Polystyrene.............................................................................................................113Engineering Resins ................................................................................................114Fibers......................................................................................................................115

Chapter 6. High-Volume Organic Chemicals

...................................................117High-Volume Organic Chemicals..........................................................................118

Raw Material Sources ..................................................................................1181999 U.S. Annual Production ......................................................................119

Ethylene (CH

2

=CH

2

)..............................................................................................120Ethylene Derivatives ..............................................................................................121

Ethanol .........................................................................................................122Ethylene Oxide.............................................................................................123Vinyl Chloride..............................................................................................124Ethylbenezene and Styrene..........................................................................125

Propylene (CH

3

CH=CH

2

) .....................................................................................126Propylene Derivatives ............................................................................................127

Acrylonitrile .................................................................................................128Propylene Oxide...........................................................................................129Isopropylbenzene..........................................................................................130Epichlorohydrin............................................................................................132

Butadiene (CH

2

=CH-CH=CH

2

).............................................................................134Butadiene Derivatives ............................................................................................135

Hexamethylenediamine ................................................................................136Cyclooctadiene and Cyclododecatriene.......................................................137

Benzene (C

6

H

6

)......................................................................................................138Benzene Derivatives ..............................................................................................140

Cyclohexane .................................................................................................141

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Nitrobenzene and Aniline ............................................................................143Maleic Anhydride.........................................................................................144

Xylenes (C

6

H

4

(CH

3

)

2

)............................................................................................145Xylene Derivatives.................................................................................................146

Phthalic Anhydride (from o-Xylene)...........................................................146Terephthalic Acid and Dimethyl Terephthalate ...........................................147

Chapter 7. Environmental Protection and Waste Disposal ............................149

Environmental Protection ......................................................................................150Types of Possible Environmental Pollution by the Chemical Industry................151

To the Air .....................................................................................................151To Water .......................................................................................................151

Methods of Pollution Control................................................................................152Pollution Control Laws and Regulations ..............................................................153Partial History of Pollution and Pollution Control by the Chemical Industry ....154

Information Sources

............................................................................................157

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1

Introduction

The objective of this chapter is to provide a basis for some understandingof chemistry and the chemical industry. Segments and characteristics of theindustry together with important events in chemical history are briefly pre-sented. The “language” of chemistry is introduced and important chemicalterms are defined.

1

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2

Chemistry and the Chemical Industry

CHEMICAL AND ALLIED PRODUCTS INDUSTRIES

I

MPORTANT

S

EGMENTS

Inorganic chemicalsPetrochemicalsSynthetic resins and plasticsTextile fibersSynthetic rubberPharmaceuticals and drugsSoap, detergents, and cosmeticsPaint, varnishes, and printing inksFertilizers and other agricultural chemicalsAdhesives and sealantsDyes and pigmentsPaperGlass

In terms of total product value, the worldwide shipments of the chemicaland allied products industries were almost 1600 billion dollars in 1999. Inthe U.S. alone, the value was 435 billion dollars (source:

Chemical & Engi-neering News

, June 26, 2000). The U.S. has the largest chemical economyby far of any country in the world, followed by Japan and Germany as distantsecond and thir

d.



Introduction

3

CHEMICAL INDUSTRY

C

HARACTERISTICS

Large, diverse, and complexGlobalStrong technology baseMany segments, highly fragmentedSubject to business cyclesHighly competitiveCapital intensiveCommitted to research and developmentAdvanced in use of computers and computer controlsOver 50% of the products are based on petroleumBest employee safety record among all major industriesCriticized for many environmental problems

Because of the absolute necessity for chemicals in almost every manufac-turing industry, it is difficult to define exactly what the chemical industry is.A good definition, however, is that the chemical industry consists of allcompanies engaged in converting raw materials obtained from the environ-ment (air, ore, petroleum, trees, crops, etc.) into chemical intermediates plusthe companies that convert these intermediates into consumer end products.Chemicals derived from petroleum or natural gas, known as

petrochemicals

,comprise about 55% of the total chemicals produced. Some of the global-ization of the chemical industry now taking place is due to the shifting ofproduction by petrochemical producers to energy-rich regions of the worldsuch as Indonesia, Mexico, and the Middle East.



4


CHEMICAL INDUSTRY

T

HE

B

EGINNINGS

Pre-1600 Alchemists sought to turn base metals (iron, zinc, lead) into gold using the four “elements”— earth, fire, air, and water.

About 1600 The idea of the four “elements” was challenged and the chemical era began.

1600s Robert Boyle worked out scientific experimental methods and published his findings (the scientific method).

1700s Joseph Priestly discovered oxygen.Antoine Lavoisier distinguished between chemical and

physical changes and enumerated and verified the fundamental law of the conservation of mass.

1800s Dmitri Mendeleev published the Periodic Table of the Elements.

Ancient man (prehistoric–600 BC) practiced certain chemical arts such asextraction and working of metals, manufacture of leather, production ofalcoholic beverages, and the use of vegetable oils, alkaloids, and narcotics.The Greek philosophers (600–200 BC) speculated on problems in the realmof what we now call chemistry, but they did little or no experimentation. Inthe Dark and Middle Ages, alchemy flourished and gradually evolved intoan experimental science as the result of the thinking of men such as RogerBacon (1214–1294), Paracelsus (1493–1541), and Francis Bacon(1561–1626). The birth of modern chemistry as an exact science, based onthe law of the conservation of mass and on the quantitative study of chemicalreactions, is dated from the work of Lavoisier.



Introduction

5

CHEMICAL INDUSTRY

R

ESEARCH

AND

D

EVELOPMENT

/E

NGINEERING

T

ECHNOLOGY

Important base for chemical industry:R&D spending for 2000 was over $250 billion.Most of the R&D in the U.S. is funded and carried out by the chemicalindustry.High investment facilities required with modern (state-of-the-art)

scientific equipment.R&D activities:

Basic chemical research (by trained chemists); much of this is donein universities

Improve existing products (e.g., better quality)Improve existing processes (by chemists and engineers), including

cost reductionsBy-product disposal and utilizationSolution of environmental problems

The size of today’s chemical industry is a result of research and development(R&D) activities that generated new products and processes resulting in rapidindustry growth. Over the years, R&D emphasis shifted from basic researchaimed at new chemicals and their uses to improvement of existing productsand processes. Today, substantial R&D is directed toward solving problemsrelated to the environment and to satisfying governmental regulations.



6


CHEMICAL INDUSTRY

H

ISTORY

Pre-1900 Cement, lye, soap, explosives, dyes, paint, fertilizer, chemicals based on coal

1920s–30s Cellophane and rayon (based on wood), medicinals, photographic chemicals, nylon, plastics

1940s Synthetic rubber, pesticides, plastic films, chemicals based on petroleum

1950s Engineering plastics, preservatives, new catalysts1960s Foreign investment, lower prices, performance improvements,

pollution awareness1970s Energy and feedstock problems, higher raw materials costs1980s Imports, environment, and health concerns1990s Global industry, governmental regulations

Industrial chemistry is barely 100 years old, but tremendous developmentswere made during that time because of advances in basic chemical and engi-neering science. These advances resulted from research efforts conductedwithin chemical industry laboratories as well as in university laboratories.During the 1950s, the nature of the industry changed from emphasis ondevelopment of totally new products to refinement of existing types ofproducts. In recent years, product refinements have been guided by concernsabout human health and protection of the environment.



Introduction

7

LANGUAGE OF CHEMISTRY

Chemical naming (nomenclature)Systematic

Chemical Abstracts

(American Chemical Society)Common (historical)“Nickname” (acronyms and trade names)

Relationship of names to chemical structureProperties (chemical, physical)Chemical formulae (chemical shorthand)Pronunciation

To be knowledgeable in chemistry, one must be familiar with its language.This language includes the naming of chemicals, both systematic and com-mon names, and the names and definitions of significant chemical andphysical properties. The relationship of chemical names to chemical struc-tures and formulae is also important. And, just as with any language, if oneis to talk chemistry, it helps to be able to pronounce the names and otherterms. Many of the terms and names needed to understand chemical “lan-guage” are introduced and defined throughout this book.

A major part in the language of chemistry is in learning the names ofthe chemicals (nomenclature). Many chemicals, particularly the more com-mon ones, are known by several different names. For example, the chemicalCH

3

CH

2

OH has the systematic name “ethanol.” The publication

ChemicalAbstracts

(American Chemical Society) also uses the name “ethanol.” Thehistorical or common name is “ethyl alcohol” or “grain alcohol.” A “nick-name” for it is just “alcohol,” and there are various tradenames, dependingon the manufacturer. For example, the Eastman Company sells it under thename of Tecsol

®

. Even trained chemists have trouble with nomenclature,which makes the use of and need for written chemical formulae commonamong chemists.



8


CHEMISTRY

P

ROPERTIES

AND

C

HANGES

Properties Characteristics of a substancePhysical properties Observable characteristics such as density, color,

smell, hardness, solubility, etc.Chemical properties Properties of a substance that cause specific behavior

during chemical reactionsChemical reaction Any change that alters the chemical properties of a

substance or forms a new substanceReactants The substances present at the beginning of a chemical

reactionProducts The substances formed in a chemical reaction

One of the important tasks of chemistry is to study how substances can beidentified or distinguished from each other, that is, a study of properties.Such studies are also essential in determining how substances can be usedin human endeavors.

There are two types of physical properties:

qualitative

properties and

quantitative

properties. Qualitative properties are those that cannot be mea-sured, such as smell or taste. Quantitative properties, on the other hand, canbe given precise mathematical values, for example, the weight of a certainvolume of a substance (density), the temperature at which the substance boils(boiling point), or electrical conductivity.

Chemical properties depend on the ways in which a substance interacts(reacts) with other substances. Sulfuric acid reacts with iron to form iron sulfateand hydrogen.

This is a chemical reaction. The fact that iron reacts when it comes intocontact with sulfuric acid is a chemical property of iron. Conversely, theability of sulfuric acid to affect iron is a chemical property of sulfuric acid.The sulfuric acid and iron are called

reactants

in the above equation, andthe iron sulfate and hydrogen are the

products

of the reaction.

Iron Sulfuric acid Iron sulfate Hydrogen++



Introduction

9

CHEMISTRY

S

UBSTANCE

S

TATES

Solid state The state (or phase) in which a substance has a definite volume and shape

Liquid state The state in which a substance has a definite volume, but can change shape

Gaseous state A state in which a substance has no definite volume or shapeMelting The change of state from solid to liquidVaporization A change of state from liquid to gaseousCondensation A change of state from gaseous to liquidSublimation The change of state from solid to gaseous without going

through the liquid state

A change of state is a physical change that does not alter chemical properties.It usually takes place by increasing or decreasing the temperature of asubstance. The ability to change the state of substances is important in thesynthesis and purification of chemicals.

Water from a tap is an example of a chemical in the liquid state, whereasice is water in a solid state. When liquid water boils, it turns to steam, whichis water in the gaseous state. A dripping icicle on a warm winter day is anexample of melting, whereby the solid phase of water (ice) is converted backto the liquid state. Droplets of water forming on a cool surface is the resultof condensation of gaseous water (steam) back to liquid water. Carbon dioxide,the gas in carbonated beverages, is known as dry ice when it is in the solidstate. When dry ice is heated, it goes directly to a gas without first becomingliquid. This is sublimation.



10


CHEMISTRY

C

HEMICAL

S

UBSTANCES

Matter All substancesElement A substance that cannot be split into simpler substances by a

chemical reactionAtom The smallest particle of an element that retains the chemical

properties of that elementCompound A combination of two or more elements held together in some

way. It has different physical and chemical properties from the elements it contains. The proportion of each element in a compound is constant, for example, the compound known as water always contains two atoms of hydrogen and one of oxygen

Molecule The smallest particle of an element or compound that existson its own and still retains its properties

All matter is composed of elements. Most matter contains two or moreelements and some in the form of compounds contain thousands or evenmillions of atoms. Water, for example, is a compound that contains twoelements: hydrogen and oxygen. The chemical compound we know as sugarcontains three elements: carbon, hydrogen, and oxygen. Table salt is com-posed of the elements sodium and chlorine.

Mixtures

are blends of two or more elements and/or compounds that arenot chemically bound to each other. Mixtures can usually be separated byphysical means.



Introduction

11

CHEMISTRY

C

HEMICAL

R

EPRESENTATION

Chemical symbol A way of expressing an

element

in written form. It represents one atom and often is the first one or two letters of the name of the element.

Molecular formula A combination of symbols representing one

molecule

of an element or compound. It shows which elements are in the molecule and the number of atoms of each element.

Reaction equation A written expression of a chemical reaction where the reacting chemicals are shown to the left of an arrow pointing to the products of the reaction on the right. Either words or formulae can be used.

Balanced equation An equation using formulae where the number of atomsof each element involved in the reaction is the sameon each side of the arrow.

The language of chemistry is understood better when the symbols of themore common elements are known, such as those shown on the followingpage. Use of these symbols provides a convenient shorthand method forchemists to represent molecular formulae. In these formulae, the subscriptnumber following the atomic symbol denotes how many atoms of that ele-ment are in the molecule, for example, the formula for water is H

2

O, whichmeans each molecule of water contains two atoms of hydrogen (symbol H)and one atom of oxygen (symbol O).

The process (chemical reaction) by which a chemical product is made,as depicted by an equation, is called

synthesis

. Working in laboratories,chemists devise new ways to synthesize known chemicals or new chemicalsnever made before and not found in nature. Synthesis chemists working inindustrial laboratories also must find or develop uses for the new chemicalsthat they synthesize while considering the costs of eventual manufacture.



12


CHEMISTRY

S

YMBOLS

OF

C

OMMON

E

LEMENTS

O Oxygen A gaseous element essential to human life; comprises about 20% of the air

H Hydrogen The most abundant element in the universeN Nitrogen Necessary element in protein; air is 80% NC Carbon All living matter contains carbon compoundsCl Chlorine Abundant element, always combined in nature with

other elementsS Sulfur Occurs free in natureNa Sodium Combined with other elements in natureP Phosphorous Combined with other elements in nature; another

element essential to life

Chemists know how much by weight of an element or a compound will reactexactly with another element or compound because the atoms of each ele-ment have an assigned weight called the atomic weight. By scientific agree-ment, each element’s atomic weight is proportional to that of carbon with anassigned weight of 12. In all chemical weight calculations, hydrogen has anatomic weight of 1 (the lightest element), while nitrogen is 14 and oxygenis 16. The molecular weight of a compound is the sum of the weights of allof the atoms in the compound as shown by its chemical formula; for example,the molecular weight of water with the formula H

2

O is 2

×

1 (2 hydrogens)

+

1

×

16 (1 oxygen), which totals 18. It is desirable for chemical calculations to deal with weighable amounts

of various substances that we know contain equal numbers of molecules.For example, the molecular weight of hydrogen is 2 and that of oxygen is 32.This means that 2 g of hydrogen contains the same number of molecules as32 g of oxygen. These actual weights are called

gram-molecular weights

or

moles

, for short. Thus, a gram-molecular weight (or mole) of any chemicalis the quantity of that chemical whose weight is numerically equal to itsmolecular weight. It has been determined that one gram-molecular weightof a chemical contains 6.023

×

10

23

molecules (this is called Avogadro’snumber).



Introduction

13

CHEMISTRY

D

IVISIONS

Inorganic The chemistry of all elements and their compoundsexcept those containing carbon

Organic The chemistry of all compounds containing carbonPhysical Applies concepts of physics to chemical phenomenaAnalytical Chemical characterization and identificationBiochemistry Chemistry of living organismsChemical engineering Design and operation of equipment for the production of

chemical products by the use of chemical reactions

No branch of science is broader than chemistry because it deals with allmatter in all forms. For convenience, chemistry is usually divided into theabove divisions, but there is a great overlap. For example, there are chemicalsknown that contain inorganic elements and large carbon compound fragmentsthat can be classified as either inorganic or organic. Thus, trained chemistsmust have a background in all the divisions of chemistry although their workmay be in a specialized area such as organic chemistry or analytical chem-istry. In the chemical industry, chemical engineers are concerned with theproduction of bulk materials from basic raw materials by large-scale appli-cation of chemical reactions worked out in laboratories. In doing this, theymake use of so-called

unit operations

of chemical engineering such as fluidflow, heat transfer, filtration, evaporation, distillation, drying, mixing, adsorp-tion, solvent extraction, and gas absorption.



14


CHEMISTRY

G

ENERAL

D

EFINITIONS

Ion An atom or group of atoms (molecule) with an electrical charge.Positively charged ions are called

cations

while negativelycharged ions are called

anions

.Acid A compound containing hydrogen that dissolves in water to produce

hydrogen ions. Hydrogen ions are positively charged.Base A compound that will react with (

neutralize

) hydrogen ions toproduce water. It is the opposite of an acid. A water-soluble baseis an

alkali

.Salt Substance in addition to water that is produced from the reaction of

an acid with a base.pH A measurement of hydrogen ion concentration (

acidity

) in water.Pure water has a pH of 7. Acids have a pH less than 7 while thepH of bases is above 7.

All chemicals, whether inorganic or organic, are either acidic, basic, orneutral. An example of an inorganic acid is sulfuric acid used in automobilebatteries, while the acetic acid found in vinegar is an organic acid. Ammoniafound in many household cleaners is a base, as are sodium carbonate andsodium hydroxide (lye). Sodium chloride (common salt) is an example of asalt because it is produced by the

neutralization

of hydrochloric acid withsodium hydroxide. A solution of table sugar in water is neutral (pH 7) becauseit does not contain hydrogen ions nor does it react with bases to producewater.

Control of pH is of critical importance in many industrial operations suchas water purification, food and drug preservation, and agriculture.



15

Important Inorganic Chemicals

Inorganic chemicals are derived from minerals in the ground or from the air,not from living matter. Some idea about the importance of this branch ofthe chemical industry is illustrated by reviewing the ten largest productionvolume chemicals, their sources, and uses.

2



16


IMPORTANT INORGANIC CHEMICALS

The chemical industry is usually viewed as being primarily associated with

organic

(carbon-containing) chemicals, largely because everyday chemicalindustry products such as plastics, synthetic fibers, drugs, etc. are derivedfrom organic starting materials. But

inorganic chemicals

are the real heartof the industry. If the production of large volume organic chemicals wereincluded in the above list, only one, ethylene, would appear (between oxygenand lime). Four of the above ten are isolated directly or indirectly from theair we breathe, so inexhaustable supplies of those four are available fromthat source. The other six are also based on readily available, inexhaustableraw materials.

These chemicals have all been produced since the beginning of thechemical industry by various and sometimes changing processes. Whenprocess changes were made, it was almost always for economic reasons,that is, to make products at lower cost. It seems unlikely that still lower costprocesses will be developed, but there may be future process changes forsome of these chemicals because of environmental concerns.

1999 UNITED STATES ANNUAL PRODUCTION

BILLIONS OF POUNDS/YEAR

0 10 20 30 40 50 60 70 80 90 100

Sulfuric acid

Nitrogen

Oxygen

Lime

Ammonia

Phosphoric acid

Chlorine

Sodium hydroxide

Sodium carbonate

Nitric acid




17

SULFURIC ACID (H

2

SO

4

)

Also known as “oil of vitriol,” “battery acid,” “oleum”

Properties

100% sulfuric acid is a colorless, odorless, dense, oily, corrosive liquid. When added to water, the mixture becomes hot enough to boil. It is a very hazardous chemical to handle because it is corrosive to all body tissues.

Commercial grades

33.5% in water (battery acid), 62.18% in water (fertilizer acid), 77.67% in water (tower acid), 98% (laboratory reagent grade)

Uses

For making fertilizer, in petroleum refining, synthetic rubber and other plastics, copper leaching, manufacture of inorganic pigments, water treatment chemicals, paints, car batteries, etc.

Suppliers

ASARCO, General Chemical, Arch Chemical, Colonial Chemical, Phelps Dodge, Kennecott Corp., Cytec Industries, El Dorado Chemical, many others.

Due to its versatile properties and low cost, sulfuric acid is the most importantproduct of the chemical industry. It is involved somewhere in the productionof almost all manufactured products. For many years, sulfuric acid produc-tion was used as an indication of the strength of a country’s economy, butnow it is more indicative of a country’s agricultural vitality because of itshigh use in the manufacture of fertilizers.

Manufacture

catalystS

+

O

2

SO

2

sulfur oxygen sulfur dioxide

catalystSO

2

+

O

2

SO

3

sulfur dioxide oxygen sulfur trioxide

SO

3

+

H

2

O H

2

SO

4

sulfur trioxide water sulfuric acid



18


Although very corrosive, it can be stored and shipped in steel or commonalloys at commercial concentrations. In some chemical processes, it is usedsimply as an acid while in others it is used as a

dehydrating agent

to removewater, as an agent to increase the rate of a chemical reaction (catalyst), oras a solvent for reactions in which it remains unchanged. It rarely ends upin the final product. Waste sulfuric acid can be recycled.

Sulfur is a yellow, relatively low melting solid. Traditionally it has beenobtained from underground deposits where it is melted in place with steamand then pumped out in a fairly pure state. Newer sources are metal ores ornatural gas where the sulfur exists in a chemically combined state.

In the most common process for making sulfuric acid, sulfur is burnedat a very high temperature in dry air to make sulfur dioxide, which is thenreacted with more oxygen over a catalyst to make sulfur trioxide. Reactionof sulfur trioxide with water produces sulfuric acid.




19

NITROGEN (N

2

)

Properties

Nitrogen is a colorless, odorless gas making up about 78% of the air. It can be liquified under pressure. At normal temperatures, it is unreactive (inert).

Commercial grades

Various purities (with respect to oxygen content) as gas or liquid.

Uses

Manufacture of ammonia, inert atmosphere for chemical reactions, metal treating, enhanced oil recovery, food processing (freezing), electronics.

Manufacture

Filtered air is compressed and cooled to remove water and carbon dioxide. The oxygen/nitrogen mixture is further cooled in a distillation column and the lower boiling nitrogen distilled from the higher boiling oxygen.

Suppliers

Air Liquide America Corp., Air Products, BOC Gases, Praxair.

Many of nitrogen’s uses depend on the fact that it is chemically inert, thatis, it does not readily react with other chemicals. The exception to this, and avery important exception, is its reaction with hydrogen at high temperatureover a catalyst to make ammonia (NH

3

). This is called

nitrogen fixation

andis one of the most important processes in the chemical industry because itprovides the nitrogen contained in almost all synthetic chemicals containingchemically combined nitrogen and all nonorganic fertilizer. Thus, the nitro-gen compounds, such as ammonia, that farmers use to stimulate crop growthcome indirectly from the air.



20


INORGANIC NITROGEN COMPOUNDS

Source of hydrogen

These equations show how nitrogen from the air ends up in so many otherchemical products. It would be hard to imagine what the world would belike if no one had discovered how to convert nitrogen from the air to usablechemicals.

The hydrogen for reaction with nitrogen in the air is obtained by reactingmethane (from natural gas found in underground deposits) with water, asshown in the above equation.

H2 N2 NH3

catalyst+ Ammonia

NH3 HNO3

O2Nitric acid

NH3 HNO3 NH4NO3+ Ammonium nitrate (fertilizer)

NH3 CO2 NH2CONH2+ Urea (fertilizer)

NH3 H2SO4 NH4( )2SO4+ Ammonium sulfate (fertilizer)

CHnatural

gas

4 H2Owater

CO +synthesis

gas

H2 COcarbon dioxide

2 H2hydrogen

H2O+ +




21

OXYGEN (O

2

)

Properties

Oxygen is a colorless, odorless, and tasteless gas, that makes up about 21% of the Earth’s atmosphere. It is essential to life for almost all living matter. It is found in nature in combination with all elements except the so-called rare gases (helium, argon, and neon). It can be liquefied under pressure.

Commercial grades

Shipped at a minimum 99.5% purity as a liquid in steel cylinders. Available as pure as 99.995%.

Uses

Metallurgy (e.g., making steel), metal fabrication, chemical manufacture, medical and life-support applications, sewage treatment, rocket propellant, paper bleaching.

Manufacture

By distillation of liquid air, the same as nitrogen. Most oxygen is used captively, less than 20% of production being sold on the merchant market.

Suppliers

Air Liquide America Corp., Air Products and Chemicals, BOC Gases, Praxair.

Chemical reactions in which oxygen atoms become attached to otherelements are termed

oxidations

. Such reactions almost always result in therelease of energy in the form of heat. Some oxidations are rapid, like theburning of wood or natural gas, with the evolution of heat and light. In thiscase, the oxygen combines with the carbon in the materials being oxidized(burned) to form carbon dioxide.

Other oxidations, like the rusting of iron at room temperature, proceedslowly with a slow release of heat. In the case of iron, the final product isiron oxide (rust).

CH4 2O2 CO2 2H2O Heat+ + +



22


If iron is heated in pure oxygen to the point of rapid oxidation, a temperaturehigh enough to melt concrete can be achieved. However, whether the oxidationgoes slowly or rapidly, the amount of heat given off in the combination of thesame amount of iron with oxygen is the same.

When oxygen is removed from a chemical compound in chemical reac-tions, instead of being added to it, the reactions are called

reductions

. Thus,oxidation and reduction can be considered to be opposite chemical processes.

4Fe 3O2 2Fe2O3+




23

LIME (CaO)

Also “quicklime,” “unslaked lime,” and “calcium oxide.” “Hydrated” limeis calcium hydroxide (Ca(OH)

2

).

Properties

White to grayish-white solid. Reacts with water to form calcium hydroxide.

Commercial grades

Commercial lime is available in lump, pebble, ground, and pulverized forms.

Uses

One of the oldest commercial chemicals. Used in hundreds of applications. The most important uses are for making steel and chemicals, water treatment, pollution control, pulp and paper, and construction.

Manufacture

Limestone (calcium carbonate, CaCO

3

) from mines or quarries is heated in a kiln (calcined).

Suppliers

Barium & Chemicals, Bruchem, Chemical Lime Co., Coyne Chemical, Kraft Chemical, Austin White Lime Co., Cutler-Magner Co., Mississippi Lime Co., Los Angeles Chemical, others.

Lime has been manufactured for more than 2000 years and was the productof one of the first chemical processes used in the U.S. by the early settlers(the manufacture of rum being another). The many uses of lime are so variedthat limestone and lime production are greater than any other natural sub-stance. It is a low-cost commodity in the U.S. because there are limestonedeposits in many parts of the country. Lime plants are always close to thelimestone source in order to minimize freight costs.

CaCOlimestone

3 CaOheat

CO2carbon dioxide

+



24


AMMONIA (NH

3

)

Properties

Ammonia is a colorless gas with a suffocating, pungent odor. It is readily liquefied under pressure. The gas is very soluble in water to produce ammonium hydroxide, also known as ammonia water or aqua ammonia.

Commercial grades

Shipped as a liquid in steel cylinders under pressure.

Uses

Mainly for the manufacture of nitric acid, urea, and ammonium salts, all of which are used in fertilizers and explosives. Urea is also used in the manufacture of plastics.

Manufacture

Suppliers

There are dozens of suppliers, some of which are Air Products and Chemicals, Cytec Industries, LaRoche Industries, Coyne Chemical, Hill Brothers Chemical, and J.R. Simplot Co.

The production of ammonia is extremely important because of the need togrow ever-increasing amounts of food to feed the world’s population. It wasfirst recognized about 1840 that the application of nitrogen-containing chem-icals such as nitrates to farmland substantially increases crop yields. Thereare no abundant nitrate ores from which nitrogen fertilizers can be made.However, in the early 1900s, a German named Haber demonstrated in hislaboratory that normally unreactive nitrogen in the air can be combined withhydrogen under pressure over a catalyst to produce ammonia. The first plantto make ammonia by the

Haber process

was started in 1913. Haber receiveda Nobel Prize in 1919 for his work. About 75% of the synthetic ammoniaproduced is used in fertilizers, while 20% is used within the chemicalindustry. The other 5% goes into the manufacture of explosives and gun-powder.

3Hhydrogen

2 N2+ 2NH3nitrogen

catalyst




25

PHOSPHORIC ACID (H

3

PO

4

)

Also “orthophosphoric acid”

Properties Pure phosphoric acid is a colorless solid melting at 42°C. Soluble in all proportions in water. Commercial 85% phosphoric acid in water is a colorless, odorless, heavy liquid.

Commercial grades 75%, 89%, 85%, 105–117% in technical, food, and electronic grades.

Uses The highest value inorganic acid marketed in the U.S. and second in value to sulfuric acid. Used primarily for the preparation of salts used as fertilizers (ammonium and calcium salts), water softeners and detergents, animal feeds, and baking powder. Food-grade phosphoric acid is used to acidify soft drinks, e.g., Coca Cola. Organic phosphates are used in flame retardants.

Manufacture Mined phosphate rock is reacted with sulfuric acid. The product phosphoric acid is isolated as a 28–35% solution by filtering off the insoluble calcium sulfate co-product.

Suppliers Albright and Wilson, Coyne Chemical, FMC Corp., General Chemical, Hoechst, Monsanto, Rhone Poulenc, Texas Gulf, others.

The element phosphorus, like nitrogen, is essential to plant and animal life.Although phosphorus was not identified and isolated until 1669, phospho-rus-containing materials have been used as fertilizers since ancient times,usually from bird droppings, fish, and bone. The first phosphoric acid wasmade by treating bone ashes with sulfuric acid. This marked the beginningof the commercial fertilizer industry. Eventually, mined phosphate rock, apoor fertilizer by itself, was substituted for bones as a raw material forphosphoric acid in the mid-1880s.

Ca3 PO4( )phosphate

rock

2 3H2SO4sulfuric

acid

2H3PO4 3CaSO4gypsum

+ +



26 Chemistry and the Chemical Industry

CHLORINE (Cl2)

Properties A greenish-yellow gas with a characteristic pungent odor. Forms compounds with virtually all elements. Strong oxidizer. Slightly soluble in water. Can be readily liquified under pressure. Very toxic.

Commercial grades Shipped under pressure as a liquid in small and large steel cylinders, tank cars, barges, and pipelines.

Uses Chlorine is used for water purification and in decreasing amounts for pulp and paper bleaching. Some is used for metallurgical purposes such as metal extraction. Its largest use is for the production of organic compounds used in plastics, pesticides, herbicides, refrigeration fluids, solvents, and others.

Manufacture Co-produced with sodium hydroxide by the electrolysis of salt brine.

Suppliers Dow Chemical, OxyChem, PPG Industries, Formosa Plastics, Olin, Vulcan, Georgia Gulf, LaRouche Industries, Bayer, others.

Chlorine and sodium hydroxide are produced at the same time in a ratio toeach other that cannot be changed. This is OK for the manufacturers as longas the demand for each of these products is the same. But that usually is notthe case. If the demand for chlorine is low, producers decrease productionbecause it is difficult to store chlorine. This causes sodium hydroxide to bein short supply, and prices rise, causing some users to turn to alternates suchas sodium carbonate. When the demand for chlorine is high and sodiumhydroxide is plentiful, prices for sodium hydroxide may fall if demand failsto meet supply.

electricalcurrent

2NaCl + 2H2O 2NaOH + H2 + Cl2sodiumchloride

water hydrogen chlorine



Important Inorganic Chemicals 27

Chlorine is used to make laundry bleach, such as Clorox, by dissolvingchlorine in sodium hydroxide to give a weak solution of sodium hypochlorite.Sodium hypochlorite slowly releases an active form of oxygen, which reactswith many forms of soil and dirt to destroy them by oxidation. Sodiumhypochlorite also rapidly destroys bacteria, viruses, and molds.




SODIUM HYDROXIDE (NaOH)

Commonly known and sold as “caustic soda”

Properties Pure sodium hydroxide is a white crystalline solid. It dissolves in water with high evolution of heat and is a very strong base. It reacts with certain metals such as aluminum and zinc to produce hydrogen. Extremely hazardous chemical.

Commercial grades Sold as a solid in pellet and flake forms in several purity grades. Commonly used in commerce as a 50% solution in water.

Uses Chemical manufacture, soaps and detergents, petroleum, food processing, pulp and paper industry, water treatment, textile manufacture.

Manufacture Electrolysis of salt brine:

Suppliers Arch Chemicals, Brown Chemical, Coyne Chemical, LaRouche Industries, PPG Industries, FMC Corp., many others.

Sodium hydroxide is an important chemical raw material because itreadily forms other chemicals (salts), that are soluble in water. It is a typeof chemical referred to as a base. Bases are compounds, that react withacids to form water and a salt.

Soap is a salt made by reacting animal fats with lye, another name fora solution of sodium hydroxide in water. In the 1800s, the need for soap asthe population expanded created a demand for sodium hydroxide. Thus,sodium hydroxide was another early product of the chemical industry. Otherwashing compounds can be made by treating phosphoric acid (or boric acid)

2NaClsodium chloride

2H2O 2NaOH H2 Cl2hydrogen chlorinewater

+ +

electrical current

+




with sodium hydroxide. Such reactions are called neutralizations, the chem-ical term for the reaction of an acid with a base to form a salt and water.

Some metals that are chemically combined with oxygen (metal oxides)also dissolve in sodium hydroxide. For example, aluminum ore (known asbauxite) is treated with sodium hydroxide to isolate pure aluminum oxide,from which pure aluminum is obtained. Sand (silicon dioxide) will alsodissolve in sodium hydroxide to form a chemical known as sodium silicateor water glass.

H3PO4 3NaOH Na3PO4 3H2O+ +




SODIUM CARBONATE (Na2CO3)

Commercially sold as “soda ash”

Properties Sodium carbonate is a white, powdery solid moderately soluble in water to give a basic solution. It reacts with acids to produce a sodium salt and carbon dioxide.

Commercial grades Available in many grades such as “lite,” “dense,” or “fine powdered” in bags and bulk.

Uses Over 50% is used to make glass. Other uses include the preparation of chemicals (such as sodium silicate and sodium phosphate), soaps and detergents, in the pulp and paper industry, and in water treatment. Substantial amounts are exported.

Manufacture About 95% of the sodium carbonate used in the U.S. is mined, primarily in Wyoming. The ore is known as “trona” and needs only to be heated to produce commercial “soda ash.” Elsewhere in the world it is made by the “Solvay” process, which uses limestone and salt as raw materials. Calcium chloride is a by-product of the Solvay process.

Suppliers FMC Corp., Solvay Minerals, General Chemical, OCI Wyoming, IMC, TG Soda Ash.

Less than half as much energy is needed to recover sodium carbonate fromores as it is to make it synthetically. The environmental impact is also less.However, because there is a limited distribution of natural soda ash in theworld compared to the wide availability of salt and limestone, synthesis willcontinue to be a source of sodium carbonate outside the U.S.

Sodium carbonate undergoes many of the same reactions as sodiumhydroxide, for example, the formation of salts when contacted with acids.In the case of sodium carbonate, carbon dioxide gas is formed along withwater.




In some processes where either sodium hydroxide or sodium carbonate canbe used, the latter is sometimes preferred because less heat is liberated orthe sodium carbonate costs less.

H2SO4 Na2CO3 Na2SO4 H2O CO2+ + +




NITRIC ACID (HNO3)

Properties Pure 100% nitric acid is a colorless liquid when first prepared, but turns yellow when exposed to light. Has a choking odor. It is a strong, so-called oxidizing acid which under the right conditions will react energetically with virtually all organic compounds; will usually attack all metals except aluminum and some stainless steels. Very hazardous chemical.

Commercial grades Reagent grade nitric acid is 68–71% in water. Grades over 80% are called “fuming” nitric acid. Special concentration blends are available.

Uses The largest use is in the manufacture of fertilizers. It is also used to make one of the raw materials for nylon, virtually all gunpowder and explosives (nitroglycerin, nitrocellulose, TNT, ammonium nitrate, etc.) and the starting materials for polyurethane elastomers and paints.

Manufacture Ammonia is burned over a catalyst to a mixture of nitrogen oxides which when reacted with water produces nitric acid.

Producers Coyne Chemical, General Chemical, El Dorado Chemical, La Roche Industries, Los Angeles Chemical, J.R. Simplot Co.

Nitric acid is the principal reagent (chemical reactant) used to introducenitrogen into other chemicals for not only the uses listed but also for dyeand pharmaceutical intermediates, agricultural chemicals, and many others.This process is called nitration. Under conditions other than those used for

NH3ammonia

+ O2air

NO2nitrogendioxide

+ H2O

NO2 H2O+ HNO3




nitration, nitric acid is used to introduce oxygen rather than nitrogen into amolecule, for example in the manufacture of adipic acid used to make nylon.This is an example of an oxidation reaction where the nitric acid behaves asan oxidizer.




HYDROGEN (H2)

Properties Hydrogen is the lightest and most abundant element. It is a colorless, odorless gas that can be liquefied under pressure. It is highly explosive when mixed with air and burns to produce only water.

Commercial grades Supplied as liquid in steel cylinders and as a gas under pressure in pipelines.

Uses Production of ammonia and methanol, refining of metals from oxide ores, petroleum refining, hydrogenation of fats and oils, preparation of higher alcohols, and other chemicals. Most of the hydrogen produced is used captively (i.e., by its producer).

The hydrogen is separated from the carbon dioxide by contacting the mixture with a liquid chemical (monoethanolamine), which absorbs the carbon dioxide. The latter can be recovered in high purity from the monoethanolamine.

Suppliers Air Products and Chemicals, Air Liquide America, BOC Gases, Praxair.

The original source of hydrogen for chemical purposes is the splitting ofwater into its components (oxygen and hydrogen) with electricity (electrol-ysis); however, using hydrocarbons from natural gas or petroleum is lesscostly. Because hydrogen is so abundant, there is considerable speculationand research underway on ways to use it as an energy source, for example,in fuel cells to provide electricity for homes, buses, trucks, and automobiles.A fuel cell produces electricity when the hydrogen fuel combines withoxygen from the air. The exhaust is only water so fuel cells are non-polluting.In some applications, metal cylinders or tanks will be required to store thehydrogen under pressure.

H2OCH4 + H2O CO + H2 CO2 + H2natural

gaswater synthesis

gascarbondioxide

hydrogenManufacture



35

Organic Chemistry

Originally,

organic chemistry

referred to the study of chemicals and chemicalprocesses associated with living organisms. Now, however, it is the study ofall carbon-containing compounds, with the exception of carbonate salts andcarbon oxides which are still included in the study of inorganic compounds.There are well over two million known organic compounds, almost 20 timesmore than all the other known chemicals combined. This large number is dueto the unique capacity of carbon atoms to combine with other carbon atomsto form chains or rings.

3



36


ORGANIC CHEMISTRY

The study of compounds containing the element carbon.Origin—compounds formed naturally by plants or animals.Wöhler (1828) synthesized urea (an organic compound found in human

urine) from lead cyanate and ammonium hydroxide, neither of whichare found in living matter.

Organic vs. inorganic is a matter of definition rather than source.

Organic chemistry is the study of compounds containing carbon and one ormore other chemical elements. Many years ago the term “organic” was givento those compounds known to be formed by plants or animals. However, in1828, Frederick Wöhler synthesized urea (an organic compound producedby animal life) from two inorganic compounds, lead cyanate and ammoniumhydroxide. This showed that organic compounds do not have to come froma natural source, and, now by definition, organic compounds are those com-pounds that contain carbon (with the exception of amorphous carbon, graph-ite, diamond, the gases carbon monoxide and carbon dioxide, metal carbo-nyls, and inorganic carbonates formed from carbon dioxide).



Organic Chemistry

37

ORGANIC COMPOUNDS

Greater than 95% of all known chemicals contain carbon. Carbon is uniquebecause:

• Each atom combines with four other atoms• Forms chains of atoms:

Open chainsClosed chains (rings)Combination of open and closed chains

• Combines with atoms of other elements

Organic compounds make up more than 95% of all the chemical compoundsknown to exist. One reason for this is that carbon is unlike all other elements.It can form chemical bonds to connect (become bonded) with four otheratoms. This ability to connect with other atoms (form bonds) is called

valence

. Carbon is said to have a valence of 4. The most unique feature ofcarbon is that it readily forms bonds with other carbon atoms to form whatare usually called

carbon chains

. It also readily bonds to other elements,particularly hydrogen, oxygen, and nitrogen.

In addition to forming open chains, closed chains, and combinationsthereof, in recent years, it has been found that carbon atoms can even linktogether to form closed spheres, which have structures resembling soccerballs.



38


CARBON STRUCTURE

An atom is like a solar system with a heavy nucleus in the middle corre-sponding to the sun and electrons orbiting the nucleus corresponding to theplanets. There are six neutrons and six protons in the nucleus of carbon andtwo electrons in an inner orbit and four electrons in an outer orbit. The outerorbit needs eight electrons to be stable. Thus, carbon will accept an electronfrom four other atoms to complete the needed eight. Hydrogen, with oneavailable electron, needs one more electron to stabilize itself with two elec-trons. So, it can share its one electron with carbon and carbon can share oneof its electrons with hydrogen. Thus, four hydrogen atoms, each with oneelectron, can satisfy the four electrons needed by carbon. The result is astable simple organic compound known as methane.

The sharing of electrons between carbon and hydrogen is an example ofatom to-atom bonding known as

covalency

and the two-electron bond iscalled a

covalent bond

.

n Neutrons+ Protons

Electrons (carbon)x Electrons (hydrogen)

Methane

H C H

H

H

4or CH

Hydrogens

Carbon

1+

1+

1+

1+

6n6+



Organic Chemistry

39

CARBON CHAINS

Carbon atoms bond to each other to form chains, a process known as

catenation

. Open chains:

aliphatic compounds

hexane

Closed chains or rings:

alicyclic or cycloaliphatic aromatic

heterocyclic

piperidine

dioxane

thiophene

Carbon atoms can link up (bond) with other carbon atoms. When two carbons,each with three hydrogens, bond together, it forms a compound called ethane,H

3

C–CH

3

. Carbon atoms like to bond together to form chains — a processcalled

catenation

. When the carbon chains are open chains, the compoundsare called

aliphatic

compounds. Closed chains (rings) are called

alicyclic

compounds, or

cycloaliphatic

compounds. There are special ring compounds,known as aromatic compounds (Chapter 4), or rings containing other ele-ments such as oxygen, nitrogen, or sulfur. Rings containing atoms other thancarbon are called

heterocyclic

compounds.

C C C C C CH

H

H

H H

H

H H

H

H

H

H

H H

H2C

H2CCH2

CH2

CH2

H2C

HC

HCCH

CH

CH

HC

H2C

H2CNH

CH2

CH2

H2C

H2C

H2CO

CH2

CH2O

CHHC

HCS

CH



40


CARBON–CARBON MULTIPLE BONDS

Single bond ethane

Double bond ethylene

Triple bond acetylene

Carbon likes to form bonds so well with itself that it can form multiple bondsto satisfy its valence of four. When two carbon atoms are linked with a singlebond and their other valencies (three each) are satisfied by hydrogens, thecompound is ethane. When two carbons are linked by a double bond (twocovalent bonds) and their other valencies (two each) are satisfied by hydro-gens, the compound is ethylene. When two carbons are linked by a triplebond (three covalent bonds) and their other valencies (one each) are satisfiedby hydrogens, the compound is acetylene.

H C C H

H

H

H

H

H C C H

H H

H C C H



Organic Chemistry

41

ALIPHATIC HYDROCARBONS

P

ARAFFINS

(

ALKANES

,

SATURATED

HYDROCARBONS

)

• Contain only carbon and hydrogen, thus the name “hydrocarbon”

•

One carbon

methane

•

Two carbons ethane

•

Three carbons

propane

• The general formula is C

n

H

2

n

+

2

, differ by –CH

2

–

The simplest of the aliphatic hydrocarbons are the paraffins, which are alsoknown as alkanes or saturated hydrocarbons. Paraffins make up the majorcomponents of petroleum. The simplest paraffin is methane, CH

4

. Next isethane, C

2

H

6

; then propane, C

3

H

8

. Note that each of these differ by CH

2

andthat the general formula is C

n

H

2

n

+

2

where

n

is any whole number. Paraffinsmay be gases, liquids, or solids; for example, at room temperature andordinary pressure, CH

4

to C

4

H

10

are gases, C

6

H

14

to C

16

H

34

are liquids, andC

18

H

38

and higher are waxes or solids.Gasoline is a mixture of aliphatic hydrocarbons containing 6 to 11

carbon atoms (C

6

H

14

to C

11

H

24

), while kerosene is a higher boiling mixturecontaining 12 to 16 carbons.

H C H

H

H

H C C

H

H

H

H

H

H C C

H

H

C

H

H

H

H

H



42



S

TRUCTURE

Methane molecul

e

Propane molecule

The valence bonds of carbon have fixed directions and are equidistant inspace, pointing from the center to the corners of a tetrahedron forming anangle of 109

°

. Thus, in propane, which we usually write as CH

3

–CH

2

–CH

3

,the carbon atoms are not connected in a straight line, but are actually asshown in the above three-dimensional diagram.

In longer chained hydrocarbons, the carbon atoms have a zig-zag struc-ture. Also, it is important to note that the atoms are free to rotate about anysingle bond.



Organic Chemistry

43


S

TRUCTURE

:

LONG

HYDROCARBON

CHAINS

Extended chain of carbon atoms

Coiled chain of carbon atoms

Because of the atoms’ freedom to rotate about single bonds, a chain of carbonatoms can achieve various positions in space. On one extreme is the zig-zagextended chain and on the other is a coil. Such spatial structures becomeparticularly important in determining properties of very long chained com-pounds known as polymers (Chapter 5).



44


ISOMERS

Compounds with the same formula but with different structures are called

isomers

.

C

4

H

10

C

4

H

10

normal butane (n-butane) isobutane (i-butane)

The paraffin hydrocarbon containing four carbon atoms is called butane,but two 4-carbon (C

4

) paraffins are possible. The butane with its carbonsin a line is known as normal butane or n-butane. The branched chain butaneis isobutane or i-butane. Although each compound has the formula C

4

H

10

,they have different properties; for example, n-butane boils at

−

0.5

°

C whileisobutane boils at

−

11.7

°

C. n-Butane and i-butane are

isomers

of eachother. The straight-chain paraffin is always called the normal form.

CH3 CH2 CH2 CH3 CH CH3

H3C

H3C



Organic Chemistry

45

ISOMERS

With five carbons in a hydrocarbon molecule, there are three isomerswith the molecular formula C

5

H

12

:

n-pentane neopentane

isopentane

and a single ring of C

5

H

10

cyclopentane

As the number of carbon atoms increases, the number of possible isomersbecomes larger. Whereas there are only two isomeric butanes, there are threeisomeric pentanes. With five carbons, in addition to the open-chain com-pounds shown, a stable ring compound known as cyclopentane is also possible.Five- and six-membered carbon rings are very stable because the bondsbetween carbon atoms in these size rings are close to the 109

°

angle preferredby carbon. Three- and four-membered hydrocarbon rings are also known,but they are less stable because of the required distortion of the bond angle.

Note that whereas n-, neo-, and isopentanes have the same molecularformula, C5H12, and are therefore isomers, cyclopentane has the formulaC5H10, and so is not an isomer of the open-chained pentanes.

CH3 CH2 CH2 CH2 CH3

H3CC

CH3

H3C CH3

CH2 CH2 CH3

H3C

H3C

H2C CH2

CH2

H2C

H2C




PARAFFIN NAMES

CH4 MethaneC2H6 EthaneC3H8 PropaneC4H10 ButaneC5H12 PentaneC6H14 HexaneC7H16 HeptaneC8H18 OctaneC9H20 NonaneC10H22 DecaneC11H24 UndecaneC12H26 Dodecane

The ending “ane” in the name denotes a paraffinic hydrocarbon. Alkyl groupsare derived from these stand-alone molecules by the removal of one hydro-gen. For example, a methyl group, , is methane with one hydrogenremoved. The hexyl group, , is hexane with one hydrogen removed.Organic groups are not stand-alone molecules, but are always part of amolecule. The general term for a group derived from a paraffin is alkyl group.A general symbol sometimes used by chemists for an organic group is simply−R. The alkyl groups are named by replacing the “-ane” of the parentparaffinic hydrocarbon with the ending “-yl.” Thus, ethyl is the alkyl groupderived from ethane, butyl is from butane, decyl is from decane, etc.

− CH3

− C6H13



Organic Chemistry 47

PARAFFIN NAMES

1 2 3 4 5 6

2-methyl-4-isopropyl hexane

Name base: longest straight chain of carbon atomsNumbered to give the lowest sumThe alkyl groups attached to the carbon base are methyl and isopropyl

More complicated paraffinic hydrocarbons take their names from the longestchain of carbon atoms. In the name the atoms are numbered so that the sumof the atoms bearing substituent groups (side chains) is the lowest. The sidechains (alkyl groups) are described as being attached to a numbered carbonatom. In the above example, the longest straight chain is six carbons, so thecompound is a hexane with the isopropyl group attached to carbon atom 4 andthe methyl group to carbon atom 2. Had the hexane chain been numbered inreverse, the compound would be 3-isopropyl-5-methyl hexane. However,because the sum of 2 + 4 is less than 3 + 5, the correct name is 2-methyl-4-isopropyl hexane.

CH CH2 CH CH2CH3 CH3

CH3 CH CH3

CH3




PARAFFINS

The chief sources of the paraffins are natural gas and petroleum. Petroleum(also called “crude oil”) is a complex mixture of paraffins that can beseparated by a process called distillation into fractions according to theirboiling range. The C1–C4 paraffins under normal conditions are gases, C5–C17

are liquids, and C18 and higher are solids. Paraffins serve many uses to helpmankind. Perhaps most importantly, they are the building blocks from whichmost of our industrial organic chemicals are manufactured.

Boiling Range Name Carbons Use65–212°F Ligroin C5–C7 Solvents180–250°F Naphtha C6–C8 Paint thinner160–390°F Gasoline C6–C11 Motor fuel390–570°F Kerosene C12–C16 HeatingAbove 570°F Heavy oil C13–C18 Fuel oil

Lubricating oil C16–C20 LubricantPetroleum jelly C18–C22 PharmaceuticalParaffin wax C20–C30 CandlesAsphaltic bitumen

C36–C40 Asphalt, tar, coke




FUNCTIONAL GROUPS

Hydroxyl (alcohol) −OH

Carbonyl (ketone, aldehyde)

Carboxyl (acid)

Nitrile (cyano) −CNAlkoxyl (ether) −O−R (R is an alkyl group)Halide (chloride, bromide, iodide) −Cl, −Br, −IAmino −NH2Nitro −NO2

Other atoms or groups of atoms such as oxygen, nitrogen, and chlorine maybe substituted for hydrogen in an aliphatic hydrocarbon. If a hydrogen inethane is substituted with the hydroxyl group (−OH), it becomes ethylalcohol. If the hydrogen is replaced by chlorine, the compound is ethylchloride. Likewise, by replacing a hydrogen with an amino group (−NH2),ethyl amine is formed. These groups substituted for a hydrogen are calledfunctional groups because they determine most of the chemical properties(functions) of organic compounds.

CO

CO

OH




FORMULAE

Empirical formula — simplest ratio of atoms in a moleculeMolecular formula — actual number of atoms in a moleculeStructural formula — shows the order of atom linkage

Example: The compound “adipic acid” is used to make nylon and as an acidulant in “Jello”

Empirical formula: C3H5O2

Molecular formula: C6H10O4

Structural formula:

The intersection of lines in the above structural formula is understood torepresent a −CH2−

There are so many isomers possible in organic chemistry that molecularformulae alone are essentially useless. Structural formulae are the mostuseful, but, for ease in printing or writing, generally every bond is not shown.For example, the butanes can be written as CH3(CH2)2CH3 for n-butane andCH3CH(CH3)CH3 for isobutane. Various ways of depicting the structural for-mula of adipic acid are shown above. Although these formulae may appear todiffer, careful study shows that they all represent the same compound.

HO C C C C C OHC

O H

H

H

H

H

H

H

H

O

HO2CCH2CH2CH2CH2CO2H

HO C CH2 CH2 CH2 CH2 C OH

O O

HO2C(CH2)4CO2H

HOOCCOOH




PARAFFINS: CHEMICAL PROPERTIES

TYPES OF CARBON ATOMS

primary secondary tertiary quaternary(1°) (2°) (3°) (4°)

isopentane

In most paraffins there will be different numbers of hydrogens attached tothe carbon atoms. There are four types of carbon atoms with names corre-sponding to the number of bonds made with other carbon atoms or functionalgroups. These names are primary, secondary, tertiary, and quaternary, asshown above. In a compound such as isopentane, there are three primarycarbon atoms, one secondary, and one tertiary.

Chlorine reacts with a hydrocarbon by substituting for one or morehydrogens. The easiest hydrogen to remove in this manner is from a tertiarycarbon, next a secondary, and the least readily from a primary carbon. Wheremore than one type of carbon is present, as in isopentane, a mixture ofcompounds containing chlorine will be produced.

C H

H

H

C

H

H

C

H

CC H

H

H

C

H

H

C

H

C

CH3 CH2 CH(CH3)2

CH3CH2CCl(CH3)2CH3CHClCH(CH3)2 + 3HClCH2ClCH2CH(CH3)2

Cl23

1° 2° 3° 1°





CHLORINATION

Chlorocarbons from Methane, CH4

Name Use Boiling PointCH3Cl Methyl chloride Refrigerant −24°C (−15°F)CH2Cl2 Methylene chloride Paint stripper 45°C (104°F)CHCl3 Chloroform Chem. intermed. 61°C (142°F)CCl4 Carbon tetrachloride Chem. intermed. 77°C (175°F)

Paraffins react with chlorine under the influence of light, heat, or catalyststo form chlorocarbons. The chlorocarbons are important in industry becauseof their own properties and because of their use as chemical intermediatesin the synthesis of other compounds. Today, many of the chlorocarbons areregulated by federal and state agencies to limit their use because of detri-mental effects on health and the environment.

CnH2n+2 Cl2 CnH2n+1Cl HCl+ +





NITRATION

CH3CH2CH3

OXIDATION

PYROLYSIS OR “CRACKING”

2CH3CH2CH3

ISOMERIZATION

CH3CH2CH2CH3 CH3CH(CH3)CH3

Paraffins react with nitric acid at high temperatures to form a mixture ofnitroparaffins which find use as solvents.

Oxidation by reaction with oxygen in the air is a major use of paraffins.Paraffins are converted to more reactive compounds called olefins by “crack-ing” under pressure at high temperature.

An important reaction in the manufacture of gasoline is isomerization ofstraight-chain paraffins to more highly branched compounds, which havebetter fuel properties (higher octane rating).

400°C

HNO3

CH3CH2CH2NO2

CH3CH(NO2 )CH3

CH3CH2NO2

CH3NO2

CH4 O2 CO2 2H2O+ +

pressure

500°C

CH3CH=CH2 H2+

+ CH2=CH2 CH4+

catalyst




UNSATURATED HYDROCARBONS

OLEFINS (ALKENES):

• Contain only carbon and hydrogen

• Contain the group , i.e., carbon atoms joined by two bonds

• The two bonds are called a double bond, and the compound isunsaturated because it contains less hydrogen atoms than the cor-responding paraffin, which is considered saturated (with hydrogen)

• CH2=CH2 CH2=CHCH3 CH2=CHCH2CH3

ethylene propylene 1-butylene• General formula is CnH2n

One of the most important reactions in the chemical industry is the “crack-ing” (removing hydrogen) of paraffins to form olefins. Olefins are essentialstarting materials for many common products that we all use, particularlyplastics. The simplest olefin is ethylene, which can be polymerized (reactedmany times with itself ) to give polyethylene used for bottles, dishware, film,etc. The next higher olefin, propylene, can be polymerized to polypropyleneused in the manufacture of rugs, toys, kitchenware, and many other plasticobjects. Note that the names of olefins end in -ene, which denotes thepresence of a double bond in the compound.

CC



Organic Chemistry

55

OLEFINS

• Nomenclature: CH

2

=

CHCH

2

CH

3

CH

3

CH

=

CHCH

3

1-butylene 2-butylene1-butene 2-butene

• Multiple double bondsCH

2

=

CHCH

=

CH

2

1,3-butadiene or just “butadiene”• Geometrical isomers

cis-1,2-dichloroethylene trans-1,2-dichloroethylene

In naming olefins, the prefix number indicates the lower numbered carbonatom involved in the double bond, numbering from one end of the molecule.Two or more double bonds in one molecule are possible with the number ofdouble bonds indicated by “di-” for two double bonds, “tri-” for three, “tetra”for four, etc. before the “-ene” ending (e.g., butadiene).

Buta

- means fourcarbons and

diene

indicates the presence of two double bonds.Because a double bond between two carbons prevents the carbons from

rotating, isomers involving the atoms bonded to the carbons are possible, asshown above with dichloroethylene. Such isomers are called

geometricalisomers,

in contrast to the

structural isomers

discussed previously. When thesubstiuent groups are on the same side of the molecule, the compound isdesignated the “

cis

-” isomer. When the substituent groups are on the oppositeside, the compound is the “

trans

-” isomer. Like all isomers,

cis-

and

trans

-isomers have the same molecular formula, but differ in certain physical andchemical properties. For example,

cis

-1,2-dichloroethylene boils at 60

°

Cwhereas

trans

-1,2-dichloroethylene boils at 48

°

C.

C C

Cl

H

Cl

H

C C

Cl

H

H

Cl

TX544_Frame_C03.fm Page 55 Tuesday, December 4, 2001 2:25 PM



OLEFINS: CHEMICAL PROPERTIES

Olefins are very reactive compounds and, thus, are the starting materials formany products of the chemical industry. Shown above are some typicalreactions for ethylene. Other olefins undergo similar reactions. The C4 olefinsrecovered in petroleum refineries are used to make synthetic rubber, gasolineadditives, plastics, and textile fibers.

CH2=CH2 +

H2 CH3CH3 ethane

ethylene oxide

ethyl alcohol

polyethylene

sulfuric acid

ethylene glycol

ethylene dichlorideCl2 CH2ClCH2Cl

O2 CH2 CH2 HOCH2CH2OH

HOSO2OH CH 3CH2OSO2OH

CH3CH2OH

+ HOSO2OH

x CH2=CH2 [CH2 CH2 ]x+1

Ag

H2O

O

catalyst




UNSATURATED HYDROCARBONS

ACETYLENES (ALKYNES):

• Contain only carbon and hydrogen• Contain the group , i.e., carbon atoms joined by three bonds• The three bonds are called a triple bond, and the compound is

unsaturated because it contains fewer hydrogen atoms than thecorresponding paraffin, which is considered saturated (with hydro-gen)

•acetylene methyl acetyleneethyne propyne

• General formula is CnH2n−2

Acetylenes contain at least one triple bond. The triple bond is even morereactive than a double bond and, therefore, acetylene is used industrially tomake other compounds used in rubber and plastics. Acetylene burns in oxy-gen to produce a very hot flame used for welding and metal cutting (oxy-acetylene torch).

Although the current source of acetylene is petroleum, it can be manufac-tured from calcium carbide, a product of the reaction of limestone and coke(carbon). During World War II, Germany, having a shortage of petroleum, usedthe latter technology to develop a chemical industry based on acetylene.

C C−≡–

HC CH≡ HC C CH3–≡




OXYGENATED ORGANIC COMPOUNDS

Oxygen is a constituent of many organic compounds. The most commonclasses of these oxygen-containing compounds and examples of each areshown above. The letter R− is the shorthand symbol for an organic groupsuch as methyl, ethyl, butyl, etc. The rest of the molecule is the functionalgroup that characterizes the class of compound. For example, −OH(hydroxyl) is the alcohol functional group.

Class General Formula ExampleAlcohols Ethyl alcohol

CH3CH2OHAldehydes Acetaldehyde

CH3CHO

Ketones AcetoneCH3COCH3

Acids Acetic acidCH3COOH

Esters Ethyl acetateCH3COOCH2CH3

Ethers Diethyl etherCH3CH2OCH2CH3

Anhydrides Acetic anhydride

R OH

R C O

H

R C O

R

R C O

OH

R C O

OR

R O R

R C O

O

C OR CH3 C C CH3

O

O

O




OXIDATION

Partial Oxidation of Paraffins

Paraffins RCH2CH3

Alcohols RCH2CH2OHAldehydes RCH2CHO

or ketones RCOCH3

Acids RCH2COOH

Complete Oxidation

When sufficient oxygen is present, organic compounds can undergocomplete oxidation (burning) with the formation of carbon dioxide andwater. By controlling the oxidation reaction (i.e., by limiting the amountof oxygen), a series of intermediate oxidation products is obtainable. Asthe degree of oxidation of a paraffin hydrocarbon progresses, first an alcohol(−C−OH) is produced, then an aldehyde (−CH=O) or ketone ( ), thenan acid (−COOH), and finally complete oxidation.

Organic compounds O2 CO2 H2O+ +

C O=

Increasing Oxidation




ALCOHOLS

Simple alcohols:

If one of the hydrogens of a paraffin is replaced by an −OH group, thecompound is called an alcohol. The −OH group is known as a hydroxylgroup in organic chemistry (not to be confused with the hydroxide ion ofinorganic chemistry). There are three types of alcohols, depending on howmany hydrogens are on the carbon to which the −OH is attached: primary(−CH2OH), secondary (−CHOH), and tertiary (−COH).

CH3OH CH3CH2OH CH3CH2CH2OH CH3CHOHCH3

methyl alcohol (methanol)

(wood alcohol)

ethyl alcohol (ethanol)(grain alcohol)

n-propyl alcohol (propanol)

sec-propyl alcohol (isopropanol)

(isopropyl alcohol)

Isomeric alcohols:

Paraffin Isomer Type of Carbon Bond to −OH AlcoholCH3CH2CH2CH3

n-butane

Primary CH3CH2CH2CH2OH1-butanol

CH3CH2CH2CH3

n-butane

Secondary CH3CH2CHOHCH3

2-butanol

CH3CH(CH3)CH3

isobutane

Primary CH3CH(CH3)CH2OHisobutyl alcohol

CH3CH(CH3)CH3

isobutane

Tertiary (CH3)3COHtertiary butyl alcohol




POLYALCOHOLS

Dihydric alcohol or glycol (two hydroxyl groups):CH2OHCH2OHethylene glycol

Trihydric alcohol (three hydroxyl groups):CH2OHCHOHCH2OHglycerine or glycerol (common name)

Tetrahydric alcohol:

pentaerythritol (common name)

There may be more than one hydroxyl group in an organic molecule. Poly-alcohols are widely found in nature as all starchs and sugars are polyalcoholsincluding sucrose (table sugar), and all fats, both vegetable and animal, arederivatives of glycerine.

Ethylene glycol is the principal ingredient in automobile antifreeze andis also used to make polyester textile fibers such as “Dacron.” Glycerine isrecovered as a by-product in the manufacture of soap and is used in cosmet-ics. Both glycerine and pentaerythritol are also used in the manufacture ofpaint and explosives.

CHOCH2 CH2OH

CH2OH

CH2OH




MANUFACTURE OF ALCOHOLS

Methyl alcohol:

Ethyl alcohol:

Higher alcohols:

The simple alcohols were originally prepared from natural products; e.g.,the heating of wood in the absence of air (destructive distillation) producedmethyl alcohol, hence the name “wood alcohol.” It is now made from carbonmonoxide and hydrogen at high temperature and pressure over a catalyst.Ethyl alcohol made by the fermentation of sugar in the presence of naturallyoccurring yeast (making of wine) goes back to the beginning of man’s history.It is also made by the fermentation of grain or potatoes from which it getsthe name of “grain alcohol.” It is also made industrially by the reaction ofethylene with water using sulfuric acid as a catalyst. Higher alcohols aremade by reacting olefins with carbon monoxide and hydrogen (a mixturecalled synthesis gas) to produce a mixture of aldehydes, which are thenreacted with hydrogen gas over a catalyst to produce the correspondingalcohols. The latter reaction is called hydrogenation.

(1) Wood 3OHCHheat

(2) CH3OH+CO 22Hcatalyst

heat, pressure

CH

CH

(1)

(2) 22 3CH2OSO2OH

OH3CH2

CH =CH Sulfuric acid

Sulfuric acid+

+

3CH2OHyeast

water

Sugar CH

RCH=CH2 CO ++ H2 + RCH2CH2CHO

+ RCH2CH2CH2OH

catalyst

catalyst hydrogen

heat, pressureRCHCH3

CHO

RCHCH3

CH2OH




ALDEHYDES

Common aldehydes:

formaldehyde acetaldehyde propionaldehyde

Manufacture:

Aldehydes are characterized by a carbonyl group (−C=O) at the end of achain with the carbon of the carbonyl group also bonded to a hydrogen.Aldehydes can be considered to be a dehydrogenated (loss of hydrogen) oroxidized alcohol; for example formaldehyde is formed by the partial oxida-tion of methanol as shown above and acetaldehyde is formed by the partialoxidation of ethanol. Formaldehyde is a gas and is important as a fumigant.Dissolved in water, it (formalin) is used as a germicide, perservative, andembalming agent. It is also a widely used intermediate in the manufactureof certain plastics and adhesives. Acetaldehyde, a liquid, is an intermediatein the manufacture of acetic acid and acetic anhydride, both important indus-trial chemicals.

H C H

O

CH3 C H

O

CH2 C H

O

CH3

CH3OH + Air HCHO + H2O

CH CH + H2O CH3CHO =

CH2 =CH2 + Air CH3CHO

methanol

acetylene

ethylene

formaldehyde

acetaldehyde

acetaldehyde




KETONES

Common ketones:

Acetone metyl ethyl ketone methyl isobutyl ketone

Manufacture:

Ketones are characterized by carbonyl groups anywhere in a chain except atthe end, and the carbonyl carbon is bonded only to other carbons. Ketones areparticularly important as solvents in paints, particularly methyl ethyl ketoneand methyl isobutyl ketone. Most have a penetrating odor and are highlyflammable.

They are also important chemical intermediates. For example, acetone isused to make methyl methacrylate (the starting material for “Plexiglas” and“Lucite” plastics), methyl isobutyl ketone, and Bisphenol A (used in epoxyand polycarbonate resins).

CH3 C CH3

O

CH3 C CH2CH3

O

CH3 C CH2CHCH3

O CH3

+ H2

CH2 =CHCH2CH3 + H2O CH3CHOHCH2CH3

+ H2CH3 CHOHCH3

catalyst

isopropanol

butylene

methyl ethyl ketone

sec-butyl alcohol

acetone

catalyst

CH3 C CH3

O

CH3 C CH2CH3

O




ACIDS

Common acids:

formic acid acetic acid adipic acid

Manufacture:

Organic acids, known as carboxylic acids, contain the carboxyl group,COOH. They behave as acids, CH3COOH CH3COO− + H+ in water andform salts when reacted with an alkaline or basic material such as sodiumhydroxide. In salt formation, the hydrogen of the −OH group is replaced bya cation. Most carboxylic acids give a weak acid response in water, but some(e.g., Cl3C−COOH) approach the acidity of inorganic acids.

Carboxylic acids with one acid group are known as monobasic acidswhile those with two acid groups are dibasic acids. All acids with more thanone acid group are in the class of polybasic acids. The simplest organic acid,formic acid, is responsible for the irritation of bee and ant stings. Vinegar isa 5% solution of acetic acid in water. The acetic acid is responsible for thecharacteristic sour taste. Citric acid, found in citrus fruits and used in softdrinks, is a tribasic acid with three carboxylic acid groups. The dibasic acid,adipic acid, is a major component of nylon.

+ O2+

HOOC(CH2)4COOH

cyclohexane cyclohexanol cyclohexanone adipic acid

HC OH

O

CH3C OH

O

C(CH2)4CHO

O O

OH

CH3CHO + CH3COOH

CH3OH + CO CH3COOH

acetaldehyde

methanol

Air

acetic acid

acetic acid

H OH O

HNO3




ACIDS

Reactions:Salt formation

R−COOH + NaOH R−COONa + H2O

Acid chlorides

R−COOH + PCl5 R−COCl + HCl + PCl3

Acid anhydrides

R−COONa + R-COCl + NaCl

EstersR−COOH + R′−OH R-COOR′ + H2O

A few of the important reactions carboxylic acids undergo are shown above.Soap is made by reacting sodium or potassium hydroxide with long-chainacids such as C17H35COOH (stearic acid). Acid chlorides and acid anhydridesare more reactive than their corresponding carboxylic acids and are used inthe chemical industry to make various acid derivatives. A very importantindustrial reaction is the reaction of carboxylic acids (or the chlorides oranhydrides) with alcohols to form esters.

R C O

O

C OR




ESTERS

Esters are the reaction product of an acid and an alcohol with the simulta-neous formation of water.Some esters with fruity odors:

CH3COOC4H9 butyl acetate pearCH3COO(CH2)2CH(CH3)2 isoamyl acetate bananaCH3CH2COOCH2CH(CH3)2 isobutyl propionate rumC3H7COOC4H9 butyl butyrate pineapple

Note that ester names contain first the alcohol, then the acid portion and endin -ate. Thus, the ester from the reaction of ethanol with acetic acid is calledethyl acetate.

The whole range of carboxylic acids and alcohols can be reacted to formesters. They are found in a large number of natural and synthetic scents andperfumes because of their pleasant odor. Many are used as solvents for paintsand resins. Esters are converted back into the original acids and alcohols byreaction with strong bases in water in a process called saponification (soapformation),

fat soaps glycerine

or by hydrolysis (which means splitting by water).

+ NaOH +

RCOOCH2

R'COOCH

R''COOCH2

H2O

RCOONa

R'COONa

R''COONa

CHOH

CH2OH

CH2OH

CH3COOC2H5 H2O CH3COOH+ CH3CH2OH+




ESTERS

Esters from inorganic acids

Alcohols form esters from inorganic acids as shown above. Like all esteri-fications, these reactions are reversible; that is, in the presence of water andthe right conditions, they revert to the original alcohol and acid. Nitrate estersare mainly used as explosives, but some have found use as diesel fueladditives. Note the difference between a nitrate ester such as ethyl nitrate(C2H5ONO2) and an organic nitro compound such as nitroethane (C2H5NO2).

C2H5OH + H2SO4 C2H5OSO3H + H2O

C2H5OH + HNO3 C2H5ONO2 + H2O

ethanol ethyl sulfatesulfuric acid

ethanol ethyl nitratenitric acid

CH2OH

CH2OH

glycerine

CHOH + HNO3

CH2ONO2

CH2ONO2

CHONO2 + H2O

nitroglycerine(glycerine trinitrate)




ETHERS

R–O–RManufacture:

Reactions:

Epoxides (cyclic ethers):

Ethers contain the characteristic linkage −C−O−C−, that is, an oxygenbonded to two carbons. Ethers can be thought of as alcohols in which thehydrogen of the alcohol group is replaced by an alkyl group. The mostcommon ether is ethyl ether, an extremely flammable liquid boiling justabove room temperature. It was used for many years as an anesthetic formedical procedures because it causes unconsciousness when breathed, butit has now been replaced by safer chemicals. The simplest ether, methylether, is a gas used in certain aerosol sprays. The ether linkage in straight-chain compounds is quite stable, but it can be chemically broken by heatingwith acids such as hydrogen iodide (HI).

Epoxides are cylic ethers which are highly reactive because of the strainedbond angles of a three-membered ring. Because of the high reactivity ofepoxides, they are the starting materials for so-called epoxy resins used forhigh-strength adhesives.

2CH3CH2OH 3CH2 O CH2CH3 H+ 2Oethyl alcohol ethyl ether

CH

CH3 CO 3H HI7 + 3+ 7H3IHC C OHmethyl propyl ether propanolmethyl iodide

CH2 =CH2 +Air CH2 CH2

Ocatalyst

ethylene oxide

H2O

2(O

HOCH2 CH2OHethylene glycol

ethylene

)




NITROGEN-BASED ORGANIC COMPOUNDS

The most important element in organic chemistry after carbon, hydrogen,and oxygen is nitrogen. Generally, nitrogen behaves in organic compoundsas if it has a valence of three; that is, each nitrogen is bonded to three otheratoms. Amines are derivatives of ammonia (NH3). Nitro compounds arebased on oxides of nitrogen, for example, nitrogen dioxide (NO2), which isalso used to make nitric acid. Nitriles are derivatives of hydrogen cyanide(HCN). Isocyanates contain the group −N=C=O and are highly reactive, forexample, with water. Amides are formed by the reaction of carboxylic acidsor their derivatives with ammonia or amines.

Class General Formula ExampleAmines R−NH2 CH3−NH2

methyl amine

Nitro compounds R−NO2 CH3CH2NO2

nitroethane

Nitriles R−CN CH3−CNacetonitrile

Isocyanates R−N=C=O CH3−NCOmethyl

isocyanate

Amides CH3CONH2

acetamideR

OC NH2




AMINES

NH3 CH3NH2 (CH3)2NH (CH3)3Nammonia methylamine dimethylamine trimethylamine

(primary) (secondary) (tertiary)

Amines are basic and form salts with acids

Tertiary amines react with alkyl halides to form quaternary ammonium salts

Organic derivatives of ammonia are called amines. Because nitrogen istrivalent, amines can be primary (attached to one carbon), secondary(attached to two carbons), or tertiary. All amines are basic, and their strengthas bases increases with the number of alkyl groups attached to the nitrogen;that is, methyl amine is a stronger base than ammonia and trimethylamineis stronger than dimethylamine. Amines can be prepared from ammonia andan alkyl halide:

The alkyl halide (ethyl bromide in the above equation) can react furtherwith the primary amine produced to give a secondary amine and with thatto form a tertiary amine and finally a quaternary ammonium salt. Quater-nary ammonium hydroxides are very strong bases like sodium hydroxide.Tetramethylammonium hydroxide is a very important chemical used in themanufacture of semiconductors and other electronic industry products.

CH3NH2 + HCl CH3NH4Cl

methylamine hydrochloride

(CH3)3 N + CH3Br (CH3 )4 N+ Br-

tetramethylammonium bromide

C2H5Br NH3 C2H5NH3Br+

NaOHC2H5NH2 NaBr H2O+ +




AMIDES

Manufacture:

When the −OH of a carboxylic acid is replaced by an −NH2, the compoundproduced is an amide. Amides are neutral to mildly basic compounds. Theycan be made from acids, acid chlorides, acid anhydrides, and esters byreaction with ammonia or primary and secondary amines. The amide linkageis found in polyamide resins such as nylon.

Urea, NH2CONH2, is the diamide of carbonic acid, (HO)2CO, and ismanufactured in large volume for use in fertilizers and plastics by the reactionof carbon dioxide and ammonia.

ROC NH2

CH3COOH + NH3 CH3CONH2 + H2Oacetamide

CH3 23 3COCl + NH CH CONH + HCl

CH3COO + NH3 CH3CONH2 + CH3COOH

CH3CO

CH3COOC2H5 + NH3 CH3CONH2 + C2H5OH



73

Aromatic Organic Chemistry

Aromatic organic chemistry is a special branch of organic chemistry becausethe six-membered carbon rings that define aromatic compounds are excep-tionally stable and act as central supports to which other groups can beattached. The name “aromatic” was given to early isolated examples of thesecompounds because they have characteristic odors.

4



74


AROMATIC ORGANIC CHEMISTRY

Aromatic chemistry is the chemistry of six-membered carbon rings typ-ified by the parent one-ring compound.

B

ENZENE

Although the above structures satisfy the molecular formula, double bondsdo not in reality exist in aromatic compounds. Thus, aromatic rings areusually depicted by a hexagon with a circle in it. It is understood that ahydrogen is at each corner.

Benzene and related aromatic compounds were first isolated from thegases given off during the heating of coal in the absence of air to producea form of carbon known as coke, used in the manufacture of steel. Thatbenzene had the molecular formula C

6

H

6

was determined in 1825, but it tookover a hundred years to prove its structure even though its correct structurewas suggested in 1865.

H

H

H

H

H

H

H

H

H

H

H

H




75

The chemical reactions of benzene and all aromatic compounds, withfew exceptions, are unlike those of

unsaturated

aliphatic compounds (ole-fins); that is, addition reactions do not occur. Instead, the hydrogens on thering are replaced by other atoms or groups of atoms. The aromatic ringremains unchanged by these

substitution

reactions. All six of the hydrogensin benzene can be replaced by other atoms.



76



S

UBSTITUTED

B

ENZENES

When one hydrogen is replaced in an aromatic compound such as ben-zene, it is called mono-substitution.

In most cases, the mono-substituted compounds are named as derivatives ofbenzene.

Replacement of a hydrogen of benzene by chlorine is termed

chlorination

.When one or more hydrogens are replaced by an “

−

NO

2

” (nitro group), itis called

nitration

. Reaction of benzene with sulfuric acid, a reaction knownas

sulfonation

, leads to a sulfonic acid. Note that in each substitution reaction,a small hydrogen-containing compound is formed.

An organic compound can be both aromatic and aliphatic; that is, one ormore of the hydrogens of a benzene ring can be replaced by an aliphaticgroup. Such compounds are always classified as being aromatic.

Cl NO2

SO3H

H2OCl2

+

H2O+

HCl +HNO3

H2SO4

nitrobenzene

benzene sulfonic acid

chlorobenzene




77


S

UBSTITUTED

B

ENZENES

Aromatic compounds can be converted to totally aliphatic compoundsby reaction with hydrogen.

Replacement of an aromatic hydrogen by an aliphatic group is called

alkylation

and the attached group is called an

alkyl

group. Industrially,benzene is alkylated by reaction with an olefinic hydrocarbon such asethylene to make ethylbenzene, or with propylene to produce isopropylben-zene. The replaced benzene hydrogen becomes part of the attached group.

Reaction of benzene with hydrogen is one of the few cases in which benzenereacts like an aliphatic

olefin

, that is, the hydrogen appears to react as ifdiscrete double bonds were present.

methylbenzene (toluene) ethylbenzene isopropylbenzene

benzene cyclohexane

CH3 CH2CH3 CH3 CH CH3

H2

catalyst

C

CC

C

CC

H H

H H

H

H

H

H

H

H

HH



78



S

UBSTITUTED

B

ENZENES

Groups attached to aromatic rings undergo reactions similar to the samegroups in aliphatic compounds although the conditions required may bedifferent.

When aromatic compounds are reacted with hydrogen, the catalyst useddetermines which part of the molecule reacts. Thus, with the right catalyst,a

nitro

group

can be converted to an

amine

without adding hydrogen to thering. In this case the simplest aromatic amine (aniline) is produced.

Methyl groups attached to benzene rings can be reacted with oxygen toproduce aromatic carboxylic acids. Benzoic acid, the parent aromatic acid,finds wide use as a food preservative and in metal corrosion inhibitors. Aspirinand saccharin are derivatives of benzoic acid.

nitrobenzene aminobenzene (aniline)

methylbenzene (toluene) benzenecarboxylic acid (benzoic acid)

NO2

H2+catalyst

NH2

H2O+

CH3

O2+

COOH

H2O+




79


S

UBSTITUTED

B

ENZENES

The dimethylbenzenes (xylenes) are very important industrial chemicalsrecovered during the refining of petroleum. All three xylenes are used to producethe corresponding aromatic dicarboxylic acids by reaction with oxygen overa catalyst.

ortho

-Dichlorobenzene is a colorless liquid while

para

-dichlorobenzene(moth balls) is a crystalline white solid.

1,2-dimethylbenzene 1,3-dimethylbenzene 1,4-dimethylbenzene (

ortho

-xylene) (

meta

-xylene) (

para

-xylene)

chlorobenzene 1,2-dichlorobenzene 1,4-dichlorobenzene (

ortho

) (

para

)

CH3

CH3

CH3

CH3

CH3

CH3

Cl

Cl2+

Cl

Cl

+

Cl

Cl

HCl+



80



S

UBSTITUTED

B

ENZENES

Different groups can be attached to an aromatic ring, for example:

When the two groups in

disubstituted

benzenes are different, the samethree isomers are possible that are possible when the substituents are thesame. Compounds with two different substituents are usually named aspositional derivatives of a monosubstituted (parent) compound. Above, thecommon (and commercial) name for methylbenzene is toluene, and thechlorinated derivatives are named as shown above. However, the same twochlorinated derivatives can also be properly named 2-chloromethylbenzeneand 4-chloromethylbenzene. In this case, for naming, the parent compoundis methylbenzene and it is understood that the methyl group is in the 1-position. The terms “

ortho

-” (1,2-), “

meta

-” (1,3-), and “

para-

” (1,4-) are alsosometimes used; for example, 2-chlorotoluene can be called

ortho

-chlorotol-uene. This can be very confusing, but in the chemical industry, outside ofthe research labs, the common names for the parent compounds are almostalways used.

toluene 2-chlorotoluene 4-chlorotoluene

benzenesulfonic acid 3-nitrobenzenesulfonic acid

CH3

+ Cl2

CH3

Cl

+

CH3

Cl

SO3H

+ HNO3

SO3H

NO2




81


S

UBSTITUTED

B

ENZENES

When two hydrogens on a benzene ring are replaced by other elements(disubstitution), there are three possible configurations, as shown here, whereX

=

a substituent group, either the same or different.

The position of substituents on the ring and their relation to each othercorresponds to the number of the carbon to which they are attached.

Substitution of two or more hydrogens in benzene results in “positionalisomerism.” Positional isomers have the same formula, but different physicaland chemical properties. In disubstituted benzene, three positional isomers arepossible, as shown above. If the

substituents

are the same or different, one isalways listed in the 1-position. If the substituents are different, they are listedalphabetically.

1,2- or “

ortho

-” 1,3- or “

meta

-” 1,4- or “

para

-”substitution substitution substitution

X

X1

23

456

X

123

456

X

X

123

456

X



82



S

UBSTITUTED

B

ENZENES

When three hydrogens are replaced by other substituents (trisubstitution),the number of possible configurations is also three.

When different groups are present, they are numbered in ascending orderwith the main substituent always in the 1-position.

With

trisubstitution

by the same or different substituents, the three

positionalisomers

shown above are possible. When the substituent groups are the same,the positional numbers are given followed by the suffix “tri-.” For example,if the three groups are chlorine, the first isomer above is named 1,2,3-trichlorobenzene. The compound above with different substituents is namedas a derivative of the parent compound toluene (methylbenzene) where it isunderstood that the methyl group is in the 1-position.

Substitution of four benzene hydrogens by the same group (tetrasubsti-tution) also results in three positional isomers: 1,2,3,4-, 1,2,3,5-, and 1,2,4,5.

1,2,3-substitution 1,2,4-substitution 1,3,5-substitution

X

123

456

X

X

X

123

456

X

X

X

123

456

XX

CH3

NO2

Cl

2-nitro-4-chlorotoluene




83

Benzene with five hydrogens replaced are pentasubstituted, and when all sixhydrogens are replaced, the benzene is hexasubstituted.

Polymethyl-substituted benzene isomers usually are referred to by trivialnames such as pseudocumene (1,2,4-trimethylbenzene), mesitylene (1,3,5-trimethylbenzene), and durene (1,2,4,5-tetramethylbenzene). These nameswere given to these compounds when aromatic compounds were first isolatedfrom coal and their structures were as yet not proven.





POLYAROMATIC COMPOUNDS

Some aromatic compounds contain multiple benzene rings attached to eachother.

All three of these industrially important chemicals can be obtained by thecoking (heating in the absence of air) of coal. Naphthalene is also recoveredduring petroleum refining. These compounds can be converted in part orcompletely to aliphatic cyclic compounds by reaction with hydrogen. Likebenzene, the hydrogens on these aromatic ring systems can be substitutedby other groups.

Naphthalene has been used as a moth repellant and an insecticide, butthese uses are decreasing due to the increasing use of para-dichlorobenzeneinstead. Derivatives of naphthalene are used in dyes and drugs. An exampleof the latter is the pain reliever naproxen (sold in drugstores as “Aleve”).Some anthracene derivatives are also used as dyes.

naphthalene anthracene phenanthrene



Aromatic Organic Chemistry 85


CARBOXYLIC ACIDS

Benzoic acid is made by the oxidation of toluene with air (oxygen) atmoderate temperatures under conditions whereby the toluene remains as aliquid during the reaction. However, the three benzene diacids are made fromthe corresponding dimethylbenzenes (xylenes) by oxidation with air (oxy-gen) over a catalyst at high enough temperature so that the reacting xylenesare in the gaseous state. In the case of the 1,2-derivative (phthalic acid), itis not isolated as free phthalic acid (the structure shown), but rather in theform of a cyclic compound called an anhydride, which can occur with theloss of a molecule of water. This anhydride (phthalic anhydride) is usedmainly to make high-boiling organic liquids, which, in turn, are used tosoften certain types of plastic. These are called plasticizers. The odor asso-ciated with new cars is caused by these compounds. Isophthalic acid is used

benzene carboxylic acid, 1,2-benzenedicarboxylic acid,benzoic acid ortho-benzenedicarboxylic acid,

phthalic acid

isophthalic acid terephthalic acid

COOH COOH

COOH

COOH

COOH

COOH

COOH




to make fire-retardant textile fibers (“Nomex”) while terephthalic acid findsextensive use for the preparation of polyester textile fibers for clothing(“Dacron”), plastic soft drink bottles, transparent film (“Mylar”), and engi-neering plastics.





PHENOLS

Aromatic rings with attached hydroxyl groups are called phenols.

Phenol was originally recovered during the coking of coal, essentially beinga by-product. Eventually, commercial routes were developed based on ben-zene (from coal or petroleum); for example, sulfonation of benzene to ben-zenesulfonic acid followed by reaction with water to phenol plus regeneratedsulfuric acid. Phenol is used to make plastics (phenol-formaldehyde andepoxy resins) and textile fibers (nylon). Phenol is also used in solution as ageneral disinfectant for cleaning toilets, stables, floors, drains, etc. and isused both internally and externally as a disinfectant for animals.

Catechol is also obtained from coal coking and from certain wood resi-dues. Vanillin (synthetic vanilla flavoring) is a catechol derivative. Resorcinoland hydroquinone are currently made by the same type of chemistry used

isopropylbenzene, hydroxybenzene, acetone cumene phenol

1,2-dihydroxybenzene, 1,3-dihydroxybenzene, hydroquinonecatechol resorcinol

CH3 CH CH3

+ O2

OH

+ CH3CCH3

O

OH

OH

OH

OH

OH

OH




to make phenol. Hydroquinone is an important photographic chemical whileresorcinol is widely used in glues for wood (e.g., plywood manufacture).

Although phenols would appear to be alcohols, because they have an−OH group like alcohols, they do not react like alcohols but instead havethe chemical properties of acids. For example, they form salts when reactedwith a base. This is the reason that the common name for phenol for manyyears was carbolic acid.





AMINES

The largest use of aniline is for the preparation of chemicals used in therubber industry.

The diaminobenzenes are made from benzene by a combination chlori-nation–nitration route although para-phenylene diamine is also made directlyfrom aniline. ortho-Phenylene diamine is widely used for the preparation ofbiologically active compounds such as fungicides and veterinarian medi-cines. The meta-diamine is used in fire-retardant textile fibers (“Nomex”)while the para-diamine finds use in high-strength textile fibers used forbullet-proof vests, sails, army helmets, and other types of fiber-reinforcedplastics (“Kevlar”).

benzene nitrobenzene aminobenzene, aniline

1,2-diaminobenzene, 1,3-diaminobenzene, 1,4-diaminobenzene, ortho-phenylene diamine meta-phenylene diamine para-phenylene diamine

HNO3

H2SO4

NO2

H2

catalyst

NH2

NH2

NH2

NH2

NH2

NH2

NH2





BENZENE-BASED INTERMEDIATES FOR EPOXY RESINS AND POLYCARBONATES

Epoxy resins for printed circuits, castings, rocket motor casings, coatings,and adhesives are almost all made from bisphenol A. Polycarbonates basedon bisphenol A are used in glazing applications such as aircraft windows,school windows, and other areas where a combination of toughness and highclarity are required.

phenol acetone

bisphenol A

2HO + C O

CH3

CH3

HO C

CH3

CH3

OH + H2O





BENZENE-BASED INTERMEDIATES TO POLYURETHANES

Methylenedianiline is used to make an intermediate in the manufacture ofpolyurethane rubber used for making automobile parts, shoe soles, rubberwheels, and insulation foam.

aniline formaldehyde

methylenedianiline

2H2N + H2C=O

H2N CH2 NH2 + H2O



93

Polymer Chemistry

Polymers are very large organic molecules that are either made syntheticallyor are of natural origin, and find use as plastics, rubber, fibers, and coatings.Polymers were first produced commercially in 1860 by modification ofcellulose from wood or cotton, followed by a fully synthetic product madefrom phenol and formaldehyde in 1910.

5

TX544_Frame_C05 Page 93 Friday, November 30, 2001 10:12 AM


94


POLYMERS

• Giant molecules made up of repeating units called

monomers

or

mers

• Polymers are also called

macromolecules

• Differences between ordinary organic compounds and polymersare due mainly to the large size and shape of polymer molecules

• Polymers in nature• Man-made polymers

All polymers are giant molecules made up of repeating units called mono-mers or mers. These units may be the same or different. The number ofmonomers that join to form a polymer or macromolecule is called the degreeof polymerization and is theoretically infinite, but, in practice, the numberof monomer units is commonly in the range of 1000 to 20,000 if no crosslinksare present.

Polymers have been part of nature since the beginning of life. For exam-ple, proteins, nucleic acids, and polysaccharides found in plants and animalsare polymers. Today, man-made polymers are part of our lifestyle, providingclothing, paints, furniture, carpets, building materials, etc.



Polymer Chemistry

95

NATURAL POLYMERS

Starch Homopolymer of glucoseCellulose Homopolymer of glucoseChitin Polymeric acetamidoglucoseProtein Copolymer of amino acidsNatural rubber Polymer of isoprene

The subject of natural polymers is quite complex because they are involvedin the structural, circulatory, transport, protective, and reproductive systemsof all living things.

Starch

is a homopolymer of glucose in the alpha-gluco-side configuration and serves as an energy reserve for plants and an energysource of animals.

Cellulose

, a structural polymer in plants, is formed bypolymerization of glucose in the beta-configuration glucoside.

Chitin

is acellulose-like biopolymer found in the exoskeletons of many insects andmarine invertebrates (shrimp, crabs, etc.).

Proteins

, which are copolymers ofup to 20 amino acids, perform a myriad of functions in all living tissue.

Natural rubber

is the only true hydrocarbon polymer found in nature. Itrequires vulcanization (crosslinking) to give it good elastic properties.



96


POLYMER STRUCTURE

Branched polymer

Crosslinking

Branching

also occurs in polymers. The branches are extensions of linkedmonomer units that protrude from the polymer trunk chain. Branched poly-mers can also form random coils, but the branches prevent a highly irregulararrangement and, therefore, less crystallinity results because the moleculescannot line up and pack as well.

Crosslinking

means that the polymer molecules are interconnected bysome sort of bonding. The bonding can be covalent, ionic, or it can resultfrom intermolecular forces such as hydrogen bonding. With a small degreeof crosslinking, a loose network is obtained, such as in vulcanized rubber,in which the crosslinks are formed by sulfur atoms. Highly crosslinkedpolymers, such as a thermoset plastic, have such a rigid structure that whenheated they decompose or burn rather than melt. A crosslinked polymer isone super giant molecule. For example, the polymer in a bowling ball isliterally one molecule.



Polymer Chemistry

97

POLYMER STRUCTURE

Linear

Random coil

The three-dimensional shape or structure of a polymer is dependent on theshape and type of monomer and the ways the monomers are linked together.A linear polymer is one in which the monomers are connected in a chain-like manner. Although called linear, such polymers should not be thought ofas straight lines. They form random coils as seen in a plate of spaghetti.

The subscript

n

in the above formulae is a whole number indicating thenumber of monomer units in the polymer chain. This is called the polymer’sdegree of polymerization.

(CH2 CH2)n CH2 CH2 polyethylene

(CH CH2)n CH CH2

CH3 CH3

polypropylene



98


POLYMER CRYSTALLINITY

Crystallinity property effectsPolymers <100% crystallineRegularity of structure needed for high crystallinity

StretchingCold drawing

Branching decreases crystallinityCrosslinking prevents crystallinity

Crystallinity affects polymer properties, but, unlike small molecules, poly-mers are not completely crystalline. A basic requirement for crystallinity isregularity of the chain structure. Regularity allows proper alignment ofpolymer chains so that crystallization can occur. Noncrystalline regions inpolymers are called

amorphous

. Regularity can be increased by stretchingand cold drawing, because this lines up the molecules. Because branchinginhibits regularity, branched polymers tend to be less crystalline. Crosslink-ing prevents polymers from orienting to achieve the regularity required forcrystallization.



Polymer Chemistry

99

POLYMER CLASSES

Thermoplastic vs. thermosetStep growth vs. chain growthResins vs. plasticsHomopolymer vs. copolymerBlock vs. graft vs. alternating vs. randomLinear vs. branched vs. crosslinkedEnd uses

Terms used in classifying polymers can be quite confusing. As we proceedin our discussion of polymers, we will touch on each of the above terms.First, polymers can be divided into two classes based on their behavior whenheated.

Thermoplastics

soften and melt when heated. They make up about80% of man-made polymers.

Thermosets

maintain their original shape whenheated and do not soften or melt. This is due to the crosslinking of polymerchains to form giant three-dimensional molecules. Polymers may be

stepgrowth

or

chain growth,

depending on their mechanism of formation. Theterms

resin

and

plastic

refer to polymer products; however, there is muchoverlap in the usage of those terms.

Resin

is used broadly and covers naturalresins (e.g., shellac, amber, etc.) as well as polymers resulting from reactionbetween two or more substances (e.g., phenol-formaldehyde, silicones,alkyds).

Plastics

are high polymers combined with other ingredients such asplasticizers, accelerants, curatives, etc. and can be formed or molded underheat and pressure. A

homopolymer

is prepared by polymerization of a singlemonomer while a

copolymer

is prepared from two or more monomers.Copolymers may be

random,

whereby monomer A and monomer B aredistributed randomly along the polymer chain;

alternating,

whereby A andB alternate along the polymer chain;

block,

whereby the polymer chainsconsist of sequences of A connected to sequences of B; or

graft,

wherebychains of B are attached to a backbone chain of A.



100


POLYMER SYNTHESIS

Polymers are prepared by processes in which small molecules undergomultiple combinations to form very large molecules. There are two principaltypes of polymerization:

1. S

tep growth polymerization

. Important polymers manufactured bystep growth are polyamides (nylons), polyesters, andpolyurethanes.

2.

Chain growth polymerization

. Important polymers manufacturedby chain growth are polyethylene, polystyrene, polyacrylonitrile,and polymethacrylates.

Conditions that are important to all chemical reactions such as stoichiometryand reactant purity become critical in polymer synthesis. In step growth poly-merization, a 2% measuring and/or impurity error cuts the degree of poly-merization or the molecular weight in half. In chain growth polymerization,the presence of a small amount of impurity that can react with the growingchain can “kill” the polymerization.

For a polymer molecule, its molecular weight is the number of monomerunits that it consists of multiplied by the molecular weight of the monomerunit (minus the molecular weight of any by-products of the polymerization).A molecular weight of at least 5000 is normally required before the polymerdisplays useful mechanical properties.



Polymer Chemistry

101

STEP GROWTH POLYMERIZATION

Monomer + Monomer DimerDimer + Monomer TrimerDimer + Dimer TetramerTrimer + Monomer TetramerTrimer + Dimer Pentamer

M M

30-mer + 21-mer 51-mer

Condensation polymerization is the most common kind of step growth poly-merization. In condensation polymerization, the monomers link together withloss of a small molecule such as water.

Step growth polymerization is relatively slow. The reaction can be stoppedat any time and low-molecular-weight products (called oligomers) can beisolated. The monomer disappears early in the reaction because of the for-mation of the low-molecular-weight products (tetramers, pentamers, andoligomers). These low-molecular-weight products continue to react witheach other over long reaction times to build up to a fully grown polymer. Arange of molecular weights is obtained. The average of this molecular weightrange is usually taken as the polymer’s molecular weight.



102



E

XAMPLES

Polyamide

n

+

n

H

2

N–(CH

2

)

6

–NH

2

n

Polyester

n

The most common form of step growth polymerization is condensation poly-merization. Condensation polymers are generally formed from simple reac-tions involving two different monomers. The monomers are difunctional,having a chemically reactive group on each end of their molecules. Examplesof condensation polymerization are the formation of nylon 66, a polyamide,and of poly(ethylene terephthalate), a polyester. Because condensation poly-

CHO

O

(CH2)4 C OH

O

adipic acid hexamethylenediamine

–H2O C

O

(CH2)4 C NH

O

(CH2)6 NH

nylon 66

n C C

O

CH3O

O

OCH3 + n HO–CH2CH2–OH

dimethyl terephthalateethylene glycol

–CH3OHC C

O O

O CH2 CH2

poly(ethylene terephthalate)



Polymer Chemistry

103

merization proceeds stepwise, the degree of polymerization and averagemolecular weight increase as the reaction proceeds. The removal of the smallmolecules formed in the reaction is necessary to drive the reaction to comple-tion and to give high molecular weight. Monomer purity and exact propor-tions of each monomer are essential to achieve high molecular weight.



104



E

XAMPLES

Ring-opening polymerization

Polyurethane formation

Step growth polymerization can also take place without splitting out a smallmolecule. Ring-opening polymerization, such as caprolactam polymerizationto nylon 6, is an example. Polyurethane formation from a diol and a di-isocyanate is another step growth polymerization in which no small moleculeis eliminated.

n

n

HO–R–OH +

n

O=C=N–R

′

–N=C=O

NHC

O

caprolactam

NH (CH2)5 C

O

n

nylon 6

diol diisocyanate

O R O C

O

NH R′ NH C n-1H R O C

O

NH R′ NCOO

polyurethane



Polymer Chemistry

105

CHAIN GROWTH (ADDITION) POLYMERIZATION

Monomers contain double bonds and add end to endRequires an initiatorVery fast reaction — up to 10

4

times faster than condensation poly-merization

No small molecules split outExothermic

Chain growth polymerization, sometimes called

addition polymerization

,involves monomers containing a carbon–carbon double bond, CH

2

=CHX.Polymerization occurs by the propagation of the reactive site down a growingchain. The reactive site may be a free radical, an ion, or a metal complex.Once a chain is initiated, monomer units add to the growing chain veryrapidly to give a fully-grown polymer chain. During chain growth polymer-ization, heat is released. Such a reaction that releases heat is said to be

exothermic

.



106


CHAIN GROWTH (ADDITION) POLYMERIZATION

Polymerization steps:

•

Initiation

• Propagation

• Termination

Chain polymerization involves three steps. To start the reaction, a catalystthat can generate an active site, such as a

free radical

(R*), is used. In theinitiation step, the radical adds to the double bond, and the radical site ismoved to the end carbon. This new radical reacts with another molecule togive a larger radical, and the propagation reaction is underway. Usually, thenumber of monomers in the chain is greater than 1000. In the above formulae,

R* + CH2 CH

X

C*

H

X

CH2R

C*

H

X

CH2R + n CH2 CH

X

CH2CH(CH2CHR

X X

)n-1CH2 C*

H

X

CH2CH( CH2CHR

X X

)n-1 C*CH2

H

X

+ R′*

CH2CH( CH2CHR

X X

)n-1CH2CH

X

R¢



Polymer Chemistry

107

X indicates a small substituent, which may be an atom such as hydrogen (H)or chlorine (Cl) or it may be a group such as methyl (CH

3

), cyano (CN),carboxyl (COOH), carbomethoxy (COOCH3), etc. The growing chain isterminated by collision with another chain or other radical source or by oneof several other mechanisms. The number of monomer units in the polymerchain is the degree of polymerization, abbreviated DP. If the degree ofpolymerization is very low, the product is sometimes referred to as anoligomer.




TYPICAL CHAIN GROWTH POLYMERS

Polymers prepared by chain growth polymerization are very important indus-trially. Polyethylene and polypropylene are used as films and containers.Poly(vinyl chloride) serves as piping and siding for houses. Polystyrene givesvery clear, bright bottles and molded articles or may be foamed as hot drinkcups. Polyacrylonitrile is made into fibers for clothing. Polybutadiene is usedto make auto tires. Poly(methyl methacrylate) is the basis for certain autopaints and for clear glass-like objects such as auto taillights. Polytetrafluo-roethylene gives us nonstick cookware.

Polymer Name Monomer Repeating Unit

Polyethylene CH2=CH2 –CH2–CH2–

Poly(vinyl chloride) CH2=CHCl

Polypropylene CH2=CH–CH3

Polystyrene CH2=CH–C6H5

Polyacrylonitrile CH2=CH–CN

Polybutadiene CH2=CH–CH=CH2 –CH2CH=CHCH2–

Poly(methylmethacry-late)

Polytetrafluoroethylene CF2=CF2 –CF2–CF2–

CH2 CH

Cl

CH2 CH

CH3

CH2 CH

C6H5

CH2 CH

CN

C C

O

OCH3CH2

CH3

=

CH3

CCH2

CO OCH3=



Polymer Chemistry 109

COPOLYMERS

• Polymers made with two or more monomers are copolymers.• Most step growth polymers are copolymers.• Chain growth copolymers are made to achieve specific properties.• Chain growth copolymers may be:

Mixtures of two or more monomers can polymerize to form copolymers.Many copolymers have been developed to combine the best features of eachmonomer. For example, poly(vinyl chloride) (called a homopolymer becauseit is made from a single monomers) is brittle. By copolymerizing vinylchloride with vinyl acetate, a copolymer is obtained that is flexible. Arrange-ment of the monomer units in a copolymer depends on the rates at whichthe monomers react with each other. Graft copolymers are formed when amonomer is initiated by free radical sites created on an already-formedpolymer chain.

Alternating —A—B—A—B—A—B—A—B—

Random —A—A—B—A—B—B—B—A—A—B—

Block —A—A—B—B—B—B—A—A—A—B—B—

Graft —A—A—A—A—A—A—A—A—| |B B| |B B| |




POLYETHYLENE

Low-density polyethylene (LDPE): film for food packaging, etc.High-density polyethylene (HDPE): blow molded into bottles and con-

tainersLinear low-density polyethylene (LLDPE): powder coatings

Polyethylene, a thermoplastic, is the largest selling plastic material. LDPEis a branched polyethylene whose branches prevent close packing and giveslow density. HDPE is polyethylene that has essentially no branching, so themolecules pack very well, which leads to high density and high crystallinity.LLDPE is actually a copolymer prepared at low temperature and low pressurefrom a mixture of ethylene and about 10% of a C4–C8 olefin.

n C C

H

H

H

H

–(CH2–CH2–)n

n = 2500–5000




POLYPROPYLENE

Special catalyst system (Ziegler–Natta) required Three structures:

Polypropylene was not developed until the 1950s when Ziegler and Nattainvented coordination catalysts. The structural difference between polyeth-ylene and polypropylene is the methyl group in the propylene unit. Itspresence makes a difference because it makes possible three different poly-mer structures: Isotactic, with all methyl groups in the same plane makesthe best plastic; syndiotactic, in which the methyl groups alternate in thesame plane; and atactic, with the methyl groups randomly in and out of theplane is soft and rubbery. Polypropylene is used as film and in many structuralforms. It is also used as fibers for carpet manufacture and for thermalclothing.

Isotactic

Syndiotactic

Atactic

n

C C

H

H

CH3

H(CH2 CH

CH3

)n

n = 6000–20,000




POLY(VINYL CHLORIDE)

Vinyl chloride polymers and copolymers are called “vinyl resins.” Common comonomers for vinyl chloride are

O

CH2=CHOCCH3 and CH2=CCl2vinyl acetate vinylidene chloride

Poly(vinyl chloride) is usually used with a “plasticizer” to make it softer.

Poly(vinyl chloride) (PVC) is a thermoplastic that finds many uses. Rigidvinyls (unplasticized or lightly plasticized polymer) are hard and stiff andare used as pipe, house siding, and a variety of parts for construction andappliances. Plasticizers impact flexibility so that plasticized vinyls result inclear packaging films, wire and cable coverings, and upholstery materials.Plasticizers are organic compounds that are added to polymers to facilitateprocessing and increase flexibility and toughness by solvation of the polymermolecule. Among important plasticizers are nonvolatile organic liquids andlow-melting solids, for example, phthalate, adipate, and sebacate esters,tricresyl phosphate, polyols, etc. Large quantities of PVC are used to man-ufacture household and other consumer goods.

n C C

H

H

H

Cl

(CH2 C

Cl

)n

H

=




POLYSTYRENE

Polystyrene is a glassy, brittle, amorphous polymer.For many uses, it is foamed and made into egg cartons, disposable

plates and cups, food trays, packing materials, etc.Mixing polystyrene with an elastomer such as polybutadiene makes it

tougher. This material is called high-impact polystyrene.

Polystryene is an addition polymer usually made by bulk or by suspensionpolymerization. Styrene homopolymer has high rigidity, sparkling clarity,and is easy to fabricate. Styrene copolymers are very important commercially.A copolymer containing 25% styrene and 75% butadiene is known as SBRand is used for making tires, hoses, rubber-coated fabrics, and adhesives.ABS, a copolymer of 50% styrene, 20% butadiene, and 30% acrylonitrile, isa plastic that is both tough and hard. It is used to manufacture luggage, high-quality plastic pipe and fittings, telephones, appliance housings, etc.

n CHCH2CH(CH2 )n




ENGINEERING RESINS

• NylonNylon refers to polymers containing the amide, ,grouping. Nylon 6 and nylon 66 are the most common nylons. Theyare very tough and wear resistant.

• PolycarbonatesPolycarbonates are condensation polymers made from phosgene andbisphenol A. They have high impact strength and are used in glaz-ing, helmets, and appliance casings.

• PhenolicsA thermoset resin used for engineering purposes.

Engineering resins are polymers that have outstanding physical propertiessuch as thermal stability, chemical resistance, self-lubrication, weather resis-tance, etc. Generally, they are thermoplastics. They are gaining in importancein automobile manufacture as metal replacements to provide lighter weightcars.

C

O

NH




FIBERS

• NylonsNylon 66 is a condensation polymer made from adipic acid andhexamethylenediamine. Nylon 6 is made by ring-opening polymer-ization of caprolactam.

• PolyestersThe most common polyester fiber is polyethylene terephthalate(PET), prepared from ethylene glycol and terephthalic acid.

• AcrylicsPolymers of acrylonitrile, CH2=CHCN.

• PolypropylenePolypropylene fibers are mainly used in outdoor carpets and in cold-weather clothing.

Fibers are made from thermoplastic polymers. The polymers are made intofiber form, normally by extrusion of molten polymer or a polymer solutionthrough tiny holes. The resulting fiber is stretched to orient the molecules.This orientation of the molecules lines up the polymer molecules and pro-duces the strength and other properties needed in a textile yarn.



117

High-Volume Organic Chemicals

All organic chemicals are, by definition, based on chemicals derived fromliving matter. Thus, the ten highest-volume commercial organic chemicalsare all made from starting materials obtained from petroleum (oil) and naturalgas, which are believed to have been formed by the microbial decompositionof ancient marine plants and animals.

6



118


HIGH-VOLUME ORGANIC CHEMICALS

R

AW

M

ATERIAL

S

OURCES

1. Petroleum and natural gasAbout 90% of all organic chemicals produced are obtained frompetroleum and natural gas. These are nonrenewable sources, soeventually alternate raw materials will have to be utilized.

2. CoalPrior to World War II, this was the principal organic chemical rawmaterial. It is more difficult to process than oil, but most Europeancountries and the U.S. have very large coal reserves. However, itis nonrenewable.

3. Biomass (carbohydrates)Biomass includes chemicals obtained from wood, sugar, grain, etc.A totally renewable source, it will become more important in thefuture.

4. Animal and vegetable oilsChemicals from animal and vegetable oils are known as “fatty acid”products. Obviously, a renewable source.

After World War II, there was an increasing demand for gasoline and otherfuels for transportation. Oil was plentiful and cheap, both in the U.S. and inEurope. New high-capacity processes to refine gasoline made by-productsethylene, propylene, and aromatics available for chemical synthesis at a muchlower cost than previous sources, such as biomass and coal. By about 1960,gas and oil surpassed coal as the major source of organic chemicals. The priceof oil remained relatively stable while coal increased in price because itsrecovery is labor intensive. By 1970, the changeover was complete and thepetrochemical age had arrived. Now, in the U.S., organic chemical productionfrom coal is insignificant, but it remains of some importance in South Africa.




119

IMPORTANT ORGANIC CHEMICALS

All of the above high-volume organic chemicals are obtained from petroleumor natural gas. This is why the modern organic chemical industry is frequentlyreferred to as the “petrochemical industry.” The high-volume status of someof these compounds is due to their use to make others lower on the list. Forexample, ethylene is used to make ethylene dichloride, which, in turn, isused to make vinyl chloride. Ethyl benzene, made from benzene and ethyl-ene, is used to make styrene. Methyl

t

-butyl ether is made from methanoland butylene, a captive intermediate for which production data is not avail-able.

1999 UNITED STATES ANNUAL PRODUCTION

BILLIONS OF POUNDS/YEAR

0 10 20 30 40 50 60

Ethylene

Propylene

Ethylene dichloride

Benzene

Vinyl chloride

Methyl t-butyl ether

Ethyl benzene

Methanol

Terephthalic acid

Styrene



120


ETHYLENE (CH

2

�

CH

2

)

Properties

Colorless, highly flammable gas, boiling point

−

103.8

°

C (about

−

220°F). Reported to have a faint, pleasant odor.

Commercial grades

Available in technical (95%) and polymer (99.9%) grades. Transported as a gas in pipelines, as a liquid in pressurized tank cars and steel cylinders. Difficult to store.

Uses

As the largest volume organic chemical produced, it is used for the preparation of plastics (polyethylene, 50%), ethylene oxide (20%), and other plastic intermediates such as vinyl chloride and styrene.

Manufacture

Made by thermal (high-temperature) cracking in the presence of steam of any available low-cost hydrocarbon such as ethane and propane, naphthas (C

5

–C

10

), and so-called gas oils (C

10

–C

30

). Many other organic compounds are produced during the cracking step, depending on the starting material fed to the reactor (cracker).

Suppliers

BP Amoco, Chevron, DuPont, Exxon Mobil, Equistar, Phillips, Shell, Sunoco, Union Carbide, Huntsman, Dow, and others.

About 100 billion pounds of chemicals and polymers are made from ethyleneeach year. In fact, over 40% of all organic chemicals produced are based onethylene. These ethylene-based materials are found in almost every conceiv-able application encountered in daily life, for example, containers, flooring,adhesives, pharmaceuticals, oil and gasoline additives, paints, surfactants,etc.

CH3−CH3 CH2=CH2 H2+




121

ETHYLENE DERIVATIVES

About 50% of all the ethylene produced is used to make polyethylene. Thereare two main types: “high density” or HDPE and “low density” or LDPE.HDPE melts higher and is stiffer and harder than LDPE. It is also opaque,while LDPE is flexible and transparent. HDPE is used for molding bottles,housewares, toys, and for extruding pipe and conduit. LDPE is used mainlyfor packaging film. HDPE is made by a

catalytic polymerization

at relativelylow pressure while LDPE is made by polymerization at very high pressureusing a different catalyst.

Vinyl acetate is polymerized to poly(vinyl acetate), (PVAc), which findsuse in adhesives and water-based paints. Some PVAc is

hydrolyzed

(reactedwith water) to poly(vinyl alcohol) (PVA) for textile sizing, adhesives, andpaper coatings. A substantial amount of U.S.-produced vinyl acetate isexported. Prior to 1970, almost all vinyl acetate was made from acetylene.Now none of it is.

(CH2CHCl) x (polyvinyl chloride)vinyl chloride

CH=CH2 (styrene)catalyst

HOCH2CH2OH (ethylene glycol)water

CH =2 CH2 (ethylene)

WaterCH3CH2OH (ethanol)

OxygenCH2 CH 2 (ethylene oxide)

O

BenzeneCH2CH3 (ethylbenzene)

ChlorineCH2 CHCl (vinyl chloride)

OxygenCH3COOH (acetic acid)

Acetic acidCH3COOCH2 CH2 (vinyl acetate)

Ethylene(CH2CH2)x (polyethylene)

CH

=

=

3CHO (acetaldehyde)



122



E

THANOL

(Also called ethyl alcohol, grain alcohol, and industrial alcohol)

Other Methods of Preparation

Fermentation

Uses

Solvents, chemical intermediates, engine fuel.

Suppliers

Union Carbide, Pharmco Products, Grain Processing Corp. Sasol North America, Midwest Grain Products, and others.

Ethanol is the alcohol found in alcoholic beverages, such as beer, wine, gin,vodka, etc. In that form, it is produced by the

fermentation

equation shownabove, as is ethanol for use as fuel in internal combustion engines. The sourceof carbohydrates for fuel production is corn, so this use is promoted byagricultural interests. In the U.S., ethanol is added to gasoline in amountsup to 10%, but in a few countries, Brazil for example, some car engines havebeen modified to run on pure ethanol. Ethanol contains less energy thangasoline because it is already partially oxidized (contains oxygen), but itcontributes to cleaner burning fuel and less air pollution. About 10 billionpounds of ethanol were produced in the U.S. in 2000.

CH2=CH2 H2O+H3PO4 CH3CH2OH (ethanol)

C6H12O6

enzyme

glucoseCH3CH2OH CO2+




123


E

THYLENE

O

XIDE

Older Method of Preparation

Uses

Preparation of ethylene glycol for antifreeze and synthetic textile fibers (60%), hospital sterilant (15%), surfactants (10%), other chemicals (10%).

Suppliers

BASF Corp., Dow, Huntsman, Eastman Chemical, Old World Trading, Equistar Chemicals, Union Carbide, and others.

Ethylene glycol is made by reacting ethylene oxide with water:

Clothing referred to as

polyester

is made by

polymerizing

ethylene glycolwith terephthalic acid and then spinning textile fibers from the resultingpolymer. The fibers are woven into cloth from which the clothing is made.Transparent film, tire cord, and carpeting are also made from polyestersbased on ethylene glycol. It is also used for the preparation of

polyurethane

ingredients to make inline skate and scooter wheels.Many laundry and dish detergents as well as shampoos are made from

chemicals based on ethylene oxide.

CH

2

=

CH

2

+

O

2

CH

2

=

CH

2

+

Cl

2

+

H

2

O

ethylene oxide + NaCl + H

2

O

+ H

2

O

HO–CH

2

–CH

2

–OH

catalystCH2 CH2

O

CH2 CH2

Cl OH

NaOH

CH2 CH2

O



124



V

INYL

C

HLORIDE

Older Method of Preparation

Uses

Vinyl chloride is used exclusively for the preparation of plastics, by homopolymerization to poly(vinyl chloride) (PVC) and by copolymerization with other vinyl (–CH

2

=

CH–) compounds.PVC-type polymers are low-cost, fire retardant, and have good

structural properties.

Suppliers

OxyVinyls, Dow, Georgia Gulf, Formosa Plastics, Westlake.

About 10% of the ethylene produced in the U.S. is used to make vinylchloride, which in the chemical trade is usually referred to as “vinyl chloridemonomer” or VCM. The largest use of VCM is for polymerization topoly(vinyl chloride) (PVC), a thermoplastic, which in terms of volume issecond only to polyethylene. PVC is used in such diverse areas as containers,floor coverings (linoleum), plastic pipes, raincoats, and many, many others.PVC has an evironmental disadvantage over non-chlorine containing plasticsin that when it is disposed of by incineration it produces hydrogen chloride,which dissolves in atmospheric water to give hydrochloric acid. Polyethylenedoes not have this undesirable feature.

VCM is very toxic and is a known cause of a rare form of liver cancer.However, products made from it, such as PVC, pose no health threats.

CH

2

=

CH

2

+

Cl

2

+

O

2

CH

2

=

CH–Cl

+

H

2

O

CH

2

=

CH

2

+

Cl

2

Cl–CH

2

–CH

2

–Cl CH

2

=

CH–Cl

+

HCl

ethylene dichloride



High-Volume Organic Chemicals 125


ETHYLBENZENE AND STYRENE

This is a two-step reaction. The ethylbenzene is isolated in the first step andthen contacted with a different catalyst at high temperature in the secondstep. Ethylbenzene and styrene plants are usually built together.

Uses Ethylbenzene is used primarily to make styrene. Styrene is used to make polystyrene, a low-cost and versatile polymer. It is also copolymerized with other vinyl monomers to make rubber (SBR) and moldable plastics (ABS).

Suppliers Lyondell, Chevron, BP Amoco, Dow, Sterling Chemicals, Nova Chemicals.

About half of the styrene produced is polymerized to polystyrene, an easilymolded, low-cost thermoplastic that is somewhat brittle. Foamed polystyrenecan be made by polymerizing it in the presence of low-boiling hydrocarbons,which cause bubbles of gas in the solid polymer after which it migrates outand evaporates. Modification and property enhancement of polystyrene-based plastics can be readily accomplished by copolymerization with othersubstituted ethylenes (vinyl monomers); for example, copolymerization withbutadiene produces a widely used synthetic rubber.

+ CH2=CH2 + H2

benzene ethylbenzene styrene

catalyst

CH2CH3

catalyst

CH CH2




PROPYLENE (CH3CH�CH2)

Properties Colorless, flammable gas boiling at −48°C (about−54°F). Burns with a yellow sooty flame, so it can be substituted for propane in liquid petroleum gas (LPG).

Commercial grades Available in three grades: refinery (50–70%), chemical (90–92%), and polymer (99%) grade. The remaining percentage in each case is mainly propane. It is shipped as a liquid in pipelines, tank cars, tank trucks, and steel cylinders. Storage is as a liquid at pressures of about 200 psi.

Uses Used in the petroleum industry to make so-called alkylate for improved octane gasoline. Large quantities are polymerized to polypropylene for carpeting, upholstery, ropes, and other uses. Used in the chemical industry as a starting material for many large-volume chemicals such as acetone, acrylonitrile, and propylene oxide.

Manufacture Made in exactly the same way ethylene is made, that is, by cracking low-cost hydrocarbons. Plants that produce propylene are always called ethylene plants because that is the principal product.

Producers BP Amoco, Chevron, DuPont, Exxon Mobil, Equistar, Shell, Huntsman, Phillips, Dow, and others.

The production volume of propylene tracks that of ethylene because theyare simultaneously produced in the same plants. Usually, propylene sells fora somewhat lower price than ethylene, but this occasionally varies whenderivative demands change. Prices for both stay relatively constant in the25–30 cent/lb. range.




PROPYLENE DERIVATIVES

The main use of propylene is for polymerization to polypropylene, a processsimilar to the manufacture of high-density polyethylene (i.e., a low-pressure,catalytic process). Textile fibers made from polypropylene are relatively low-cost and have particularly good properties, such as high resistance to abrasionand soiling for use in furniture upholstery and indoor/outdoor carpeting.

Three major non-polymer propylene derivatives are isopropanol, acetone,and acrylic acid. Isopropanol (isopropyl alcohol) is used mainly as a solvent.It has been made from propylene by reaction with sulfuric acid and waterfor at least the last 75 years, making its manufacture the oldest, still-runningcommercial organic chemical process. It is used in household rubbing alcoholbecause, unlike ethanol, it is unfit for human consumption even in smallamounts. About 25% of the isopropanol produced is used for making acetone,in competition with a route based on isopropylbenzene.

CH2 CHCH2Cl (allyl chloride)

CH2 (acrolein)CHOCHOxygen

Chlorine

CH3CH CH2 (propylene oxide)Chlorine, water

CH (isopropylbenzene)Benzene

CH3CHCH3 (isopropanol)

CH2 CHCN (acrylonitrile)

CH3CH CH=

=

=

= =

2 (propylene)

Ammonia, oxygen

Water, H2SO4

OH

CH3

CH 3

CH2 CHCH 2Cl

O

(epichlorohydrin)O

CH2 CH COOH(acrylic acid)

O2

CH3 C CH3

O

(acetone)

CH3Propylene

(CH2CH) x (polypropylene)

O2





ACRYLONITRILE

Uses Acrylic textile fibers are primarily polymers of acrylonitrile. It is copolymerized with styrene and butadiene to make moldable plastics known as SA and ABS resins, respectively. Solutia and others electrolytically dimerize it to adiponitrile, a compound used to make a nylon intermediate. Reaction with water produces a chemical (acrylamide), which is an intermediate for the production of polyacrylamide used in water treatment and oil recovery.

Manufacture Made by the reaction of propylene with ammonia and air (the Sohio process). This is the basis for the production of all of the acrylonitrile made in the world. Recoverable and salable by-products include hydrogen cyanide (HCN) and acetonitrile (CH3CN).

Suppliers Cytec, BP Amoco, DuPont, Sterling Chemical, Solutia.

The principal use of acrylonitrile since the early 1950s has been in themanufacture of so-called “acrylic” textile fibers. Acrylonitrile is first poly-merized to polyacrylonitrile, which is then spun into fiber. The main featureof acrylic fibers is their wool-like characteristic, making them desirable forsocks, sweaters, and other types of apparel. However, as with all synthetictextile fibers, fashion dictates the market and acrylic fibers currently seemto be in disfavor, so this outlet for acrylonitrile may be stagnant or declining.The other big uses for acrylonitrile are in copolymers, mainly with styrene.Such copolymers are very useful for the molding of plastic articles with veryhigh impact resistance.

Until the 1960s, acrylonitrile was, like vinyl acetate, made from acetylene(by reaction with hydrogen cyanide), but research on catalysts in the 1950sled to the much less costly route shown above.

CH2=CH–CH3 + NH3 + O2 CH2=CH–CN + H2Ocatalyst





PROPYLENE OXIDE

Uses About 60% of the propylene oxide made is polymerized to polypropylene glycol and other polyethers for use in polyurethane foams and adhesives. Propylene glycol is also widely used in polyester resins based on maleic anhydride.

Manufacture

Suppliers Huntsman, Dow Chemical.

Most automobile and furniture seating, foam mattresses, carpet underlay-ment, and other similar products are made from polyurethanes based onpolypropylene glycol (PPG). PPG is the preferred raw material for thesetype of polymers because of the wide variation of possible properties of theend product and the relatively low cost.

CH2=CH–CH3 + Cl2 + H2O + HCl

polypropylene glycol HO–(CH2– –O–)X–H

polypropylene glycol CH3

+ NaCl + H2Opropylene glycol

CH2

Cl

CH

OH

CH3

CH|

sodium hydroxide

catalyst

CH2

OH

CH

OH

CH3water

CH2 CH CH3

O





ISOPROPYLBENZENE

(Commonly called “cumene”)

Uses Almost all of the isopropylbenzene produced is used for making phenol and acetone. The largest use of acetone is as a chemical intermediate to methyl methacrylate and along with phenol to make bisphenol A for preparation of polymers. Acetone is also used widely as a solvent.

Manufacture

Suppliers Shell, Sunoco Chemical, Aristech Chemical, Georgia Gulf, Dow Phenolchemie, Union Carbide, and others.

About a billion pounds per year of methyl methacrylate is made fromacetone, hydrogen cyanide, and methanol.

The polymerization of methyl methacrylate produces poly(methyl methacry-late), an exceptionally clear plastic sold under the names “Plexiglas” or“Lucite” as a shatter-proof substitute for glass in windows, doors, and otherglazing applications.

+ CH2=CH–CH3 +

benzene isopropylbenzene phenol acetone

+ HCN

methyl methacrylate

catalyst

CH CH3CH3

oxygen

OH

CH3 C

O

CH3

CH3 C

CH3

O

CH3 C

CH3

CN

OH

CH3OH

H2SO4

CH2 C

CH3

COOCH3




Phenol, along with formaldehyde, is used to produce a very importantand versatile group of polymers known as “phenolics” or “phenol-formal-dehyde resins.” These resins can be either thermoplastic or thermosetting,depending on the amount of formaldehyde used. A larger ratio of formalde-hyde to phenol promotes crosslinking to produce more rigid materials.





EPICHLOROHYDRIN

Uses Virtually all epoxy resins are made with starting materials based on epichlorohydrin, principally by reaction with bisphenol A. It is also used for the preparation of resins to increase the wet strength of paper. Both epichlorohydrin and glycidol are used in the manufacture of pharmaceuticals.

Manufacture

Suppliers Dow Chemical, Shell Chemical.

Epoxy resins are widely used in high-strength adhesives, corrosion-resistantcoatings, and corrosion-resistant pipes and tanks. The simplest starting mate-rial for these thermoset polymers is made from phenol, acetone (to bisphenolA), and epichlorohydrin.

CH2=CH–CH3 CH2=CH–CH2–Cl

glycidol epichlorohydrin

2 +

phenol acetone bisphenol A

HO CH 2 CH CH 2 Cl

Cl

calcium hydroxide

CH 2 CH CH 2 OH

O

CH 2 CH CH 2 Cl

O

HOCH3

C O

CH3

HO OHC

CH3

CH3

2 epichlorohydrin

O OC

CH3

CH3

CH2CHCH2

O

CH2 CH CH2

O




The final resin product is obtained by reacting (curing or crosslinking) theabove di-epoxide with acid anhydrides or polyamines. The curing agents(sometimes incorrectly called catalysts) react with the three-memberedepoxide rings to produce a highly crosslinked polymer.




BUTADIENE (CH2�CH–CH�CH2)

Properties Colorless, odorless, flammable gas, boiling point −4.7°C (23.5°F). Dimerizes thermally and forms explosive peroxides on contact with oxygen.

Commercial grades Inhibited butadiene is shipped as a liquid in tank trucks, tank cars, and steel cylinders. It is stored cold to prevent dimerization.

Uses Its largest uses are for polymeriztion to polybutadiene and copolymerization with styrene to make synthetic rubber (SBR) for tires and other rubber uses. Other uses include the preparation of chloroprene for oil-resistant rubber (neoprene) and hexamethylenediamine for the preparation of nylon.

Manufacture Some of the butadiene produced is recovered from steam crackers along with ethylene and propylene. However, most of it is now produced by the dehydrogenation of butene.

Suppliers Equistar, Texas Petrochemicals, Shell Chemical, Huntsman, Exxon Chemicals.

Butadiene is an especially versatile chemical because of its two reactivedouble bonds. It has been forecast that future butadiene supplies will beplentiful at a stable price due to an anticipated abundance of butenes. Thissuggests that butenes and butadiene are of major interest in the R&D depart-ments of many large chemical companies.

CH3–CH=CH–CH3 CH2=CH–CH=CH2 + H2catalyst




BUTADIENE DERIVATIVES

Natural rubber latex, obtained from rubber trees, is converted to its finalform by a process known as “vulcanization,” first discovered by CharlesGoodyear in 1839. Vulcanization is basically a crosslinking reaction ofdouble bonds in the latex structure with sulfur. The polymerization of buta-diene with itself or with other vinyl monomers results in a material that likenatural latex, still contains double bonds. Thus, synthetic rubber made frombutadiene can be processed and vulcanized just like natural rubber.

The first use of butadiene to make synthetic rubber was demonstrated inRussia in 1910 by S.V. Lebchev, who also developed a synthesis of butadienefrom ethanol obtained by fermentation.

The first important commercial synthetic rubber was poly(chloroprene)which was made available for sale as “Neoprene” by DuPont in 1931. It isstill made and sold today because of its superior resistance to oils, sunlight,and oxygen (ozone).

O

(tetrahydrophthalic anhydride)OCO

COMaleic anhydride

Cyclododecatriene (12-membered ring)

Cyclooctadiene (8-membered ring)

Catalyst

Catalyst

Hydrogen

Cl

CH2 CH CHC 2 (chloroprene)Chlorine

H2N CH2CH2CH2CH2CH2CH2 NH2 (hexamethylenediamine)Hydrogen cyanide

( CH CH CH CH2 CHCH )22 x (styrene-butadiene rubber)Styrene

( CH2 CH CHCH 2 )x (polybutadiene)

CH2 CH CHCH 2

Catalyst





HEXAMETHYLENEDIAMINE

Uses Most of the hexamethylenediamine produced is used for the manufacture of Type 66 nylon by polymerization with adipic acid. A minor use is for the preparation of hexamethylene diisocyanate used in light-stable polyurethane coatings.

Manufacture

Suppliers BASF Corp., Solutia, DuPont.

Type 66 nylon is a polyamide first commercialized by DuPont just prior toWorld War II. At that time, the needed hexamethylenediamine was madefrom adipic acid by reaction with ammonia to adiponitrile followed byreaction with hydrogen. The adipic acid then, like now, was made fromcyclohexane. The cyclohexane, however, was derived from benzene obtainedfrom coal. The ammonia was made from nitrogen in the air by reaction withhydrogen from water obtained in the water–gas shift reaction with carbonmonoxide from the coal. So, in the 1950s, nylon was honestly advertised byDuPont as being based on coal, air, and water.

Hexamethylenediamine is now made by three different routes: the orig-inal from adipic acid, the electrodimerization of acrylonitrile, and the addi-tion of hydrogen cyanide to butadiene. Thus, the starting material can becyclohexane, propylene, or butadiene. Currently, the cyclohexane-basedroute from adipic acid is the most costly and this process is being phasedout. The butadiene route is patented by DuPont and requires hydrogencyanide facilities. Recent new hexamethylenediamine plants, outsideDuPont, are based on acrylonitrile from propylene, a readily availablecommodity.

CH2=CH–CH=CH2 + 2HCN NC–CH2CH2CH2CH2–CNadiponitrile

catalyst

H2N–CH2CH2CH2CH2CH2CH2–NH2

hydrogen

hexamethylenediaminecatalyst





CYCLOOCTADIENE AND CYCLODODECATRIENE

Uses Cyclooctadiene is reacted with bromine to make fire-retardants. Cyclododecane is oxidized with air and then nitric acid to make a diacid containing 12 carbons. This acid is used to prepare some types of nylon, and its esters are used in synthetic lubricating oils.

Manufacture

Supplier DuPont.

Whether butadiene reacts with itself to give linear polymers or 8- or 12-carbon rings is a function of the catalyst and conditions used. Developmentof catalysts needed to give the desired products is the job of catalyst researchchemists. Although catalysis is critically important in the chemical industryand much work has been done on it in research laboratories for many years,catalyst development remains more of an art than a predictable science, andthe chemists involved in this type of research use methods they have learnedexperimentally, not from books or in classrooms.

2CH2=CH–CH–CH2 +

cyclooctadiene vinylcylohexene

3CH2=CH–CH–CH2

cyclododecatriene cyclododecane

catalystCH CH2

catalyst hydrogen

catalyst




BENZENE (C6H6)

Properties Clear, colorless, flammable liquid that boils at 80°C (176°F) and freezes at 5.5°C (42°F). It has a very characteristic odor. Recently it has been found to be toxic and is suspected of being a human carcinogen. Exposure to it should be very limited or, preferably, avoided.

Commercial grades Available in three grades: refined-535, refined-485 (nitration grade), and industrial. The numbers following the grade refer to the freezing point specification times 100. It is shipped in steel drums, tank trucks, and tank cars under heavily regulated conditions.

Uses It is used as a chemical raw material for a myriad of everyday products such as plastics, detergents, textile fibers, drugs, dyes, and insecticides. It is also found in gasoline with other aromatic hydrocarbons.

Manufacture Benzene used to be made from coal, but it is now made from petroleum by two different routes: catalytic reforming of naptha and hydrodealkylation of toluene. The first route provides toluene as a by-product for the second route.

Producers ExxonMobil, Chevron Phillips, Equistar, Koch, Dow, Citgo, BP Chemicals, and many others.

Benzene was first isolated in 1825 by Michael Faraday in London, but itsstructure remained somewhat of a mystery for over a century. In 1865, inwhat is now thought of as one of the most important pronouncements in thescience of chemistry, a German chemist by the name of August Kekulesuggested that there are alternating double bonds in the benzene ring andthat they continuously trade places with each other. In the 1930s, the latechemist Linus Pauling offered convincing evidence in favor of Kekule’stheory using a mathematical treatment known as quantum mechanics.




All steel used to be made by treating iron ore (iron oxides) with carbon.In colonial days, the required carbon (charcoal) was obtained by the heatingof wood in the absence of air. The wood was ultimately replaced by coal.To obtain carbon (coke) from coal, the coal was heated to about 2500°F.Gaseous and liquid organics distilled from the coking operation. The gaseousfraction (coal gas) was used for street-lighting in large towns. The high-boiling material (coal tar) was used for roofing and road building. The liquid(coal oil) was about two-thirds benzene along with higher aromatics. All ofthe benzene used before World War II came from this source. Now, none ofit does.

Naphtha is a mixture of aliphatic hydrocarbons isolated from petroleumby distillation. When it is passed over a catalyst under the right conditions,carbon rings are formed, followed by the splitting of hydrogen from thecarbon rings to produce benzene, toluene, and other aromatic compounds.




BENZENE DERIVATIVES

During the 1800s, benzene was of limited commercial value, finding usemainly as a solvent. But after the invention of the internal combustion engineand the automobile, it was found that motors ran better when the fuelcontained benzene. This added a new economic incentive to recover all ofthe benzene possible from the steel industry’s coke ovens. However, justprior to World War II, the importance of benzene as a chemical intermediatestarted to be recognized. These dual incentives (gasoline and chemical inter-mediate) led to new and improved benzene processes based on petrochem-istry rather than coal.

catalyst

hydrogen

ethylbenzene

styrene

cyclohexane isopropylbenzene

OH

phenol

HNO3/H2SO4

NO2

nitrobenzene

NH2

hydrogen

chlorine

oxygen

(Cl)1 6

chlorobenzenes

oxygen

maleic anhydride

aniline

CH2 CH2 CH3 CH CH2

CH CH2

CH2 CH3 CH3 CH CH3O

O

O




BENZENE DERIVATIVES

CYCLOHEXANE

Uses Over 90% of all the cyclohexane made is used to make nylon intermediates.

Manufacture

Suppliers Huntsman.

The price of cyclohexane tracks that of benzene and is only marginally higherbecause the conversion of benzene to cyclohexane is readily accomplishedin very high yield.

The subsequent reaction of cyclohexane with air in the first step to adipicacid is not simple and, actually, is not well understood chemically. Only asmall amount of cyclohexane present in the operation is allowed to reactbefore the unreacted cyclohexane is recovered for recycle and the oxygen-containing products isolated for further reaction with nitric acid. Despitedecades of research on this chemistry in efforts to increase yields anddecrease by-product formation, substantial amounts of the starting cyclohex-

+ H2

O OH

NH

O

+ +O2 (from air)

cyclohexanone cyclohexanol adipic acid

caprolactam

CH2CH2CH2CH2HOOC COOHcatalyst nitric acid

hydroxylamine rearrangement

catalyst




ane do not end up as adipic acid. Some of the by-products are useful, butadipic acid manufacturers produce many millions of pounds per year oforganic oils, which are ultimately burned as fuel because no use has beenfound for them.

About half of the nylon made in the world is made from the polymer-ization of caprolactam. Although the cyclohexanone needed to make capro-lactam can be made from cyclohexane as shown above, most of it is madefrom phenol.




BENZENE DERIVATIVES

NITROBENZENE AND ANILINE

Uses Virtually all of the nitrobenzene made is converted to aniline. The most important use of aniline is for the preparation of 4,4′-diaminodiphenyl methane (commonly called methylenedianiline or MDA), an intermediate to one of the main ingredients used to make polyurethane foams and rubber. Aniline is also used to make other rubber chemicals, textile fiber intermediates, dyes, and pharmaceuticals.

Manufacture

Suppliers BASF, Bayer, DuPont, Huntsman, First Chemical.

Up to three of the hydrogens on a benzene ring can be replaced with a nitro(−NO2) group by reaction of nitric acid in sulfuric acid. When two hydrogensare replaced by nitro in this manner (dinitration), one isomer, the meta- or1,3-, predominates. When three hydrogens are replaced (trinitration), thepredominant isomer is the 1,3,5-isomer; meta-dinitrobenzene is made bythis method as a starting material for meta-phenylenediamine, one of thecomponents in the manufacture of a heat-resistant nylon sold in the U.S.as “Nomex” by DuPont.

Obviously, polynitro- or polyaminobenzenes other than the meta-config-uration may be desirable for one reason or another. This is where the skilland training of organic chemists are required because they have learned tobe able to know and use the rules of chemistry to manipulate the shape andcomposition of carbon-containing molecules.

+ NHO3 (nitric acid) + H2

nitrobenzene aniline

H2SO4

NO2

catalyst

NH2




BENZENE DERIVATIVES

MALEIC ANHYDRIDE

Uses The largest single use of maleic anhydride is in the preparation of unsaturated polyester resins. It is first esterified with a polyalcohol (two or more hydroxyls) and then the double bond is copolymerized (crosslinked) with a vinyl monomer such as styrene to form a rigid structure. Such resins are usually reinforced with fiberglass (FRP). Maleic anhydride is also used to make oil additives and agricultural chemicals.

Manufacture

Suppliers Bayer, Huntsman, Ashland, BP Amoco.

For many years the catalytic air oxidation of benzene was the main sourceof maleic anhydride. Obviously, two carbons from each ring are wasted ascarbon dioxide in this process. Although some is still made that way, mostmodern maleic anhydride plants are based on butane oxidation. Becausebutane is forecast to be plentiful and low-cost, new routes to four-carbonchemicals from maleic anhydride are under active development.

Unsaturated polyester resins based on maleic anhydride are widely usedin coatings to manufacture boat hulls and truck caps and a variety of otheruses where a smooth, weatherproof, hard-surfaced material is desired.Because these resin types are inherently brittle, fiberglass is frequently addedfor reinforcement. Consumption of unsaturated polyesters in the U.S. is wellover a billion pounds per year, with about 50% going into construction andthe marine industry.

+ O2 (from air)

CH3CH2CH2CH3 + O2 (from air)

butane

catalyst

O

O

Ocatalyst




XYLENES (C6H4(CH3)2)

Properties There are three xylene isomers, commonly known as ortho-xylene, meta-xylene, and para-xylene. They are all colorless liquids. The ortho-isomer boils at 144°C, the meta- at 139.1°C, and the para- at 138.5°C.

Commercial grades Xylenes are available as an isomer mixture (about 10% ortho-, 72% meta-, and 18% para-) and as the pure isomers. The mixed xylenes are priced by the gallon while the pure isomers are priced per pound.

Uses The mixed xylenes are used as solvents and as octane enhancers in gasoline. The largest use for each of the pure isomers is oxidation to the corresponding dicarboxylic acid.

Manufacture The xylenes are obtained with benzene (and toluene) from the catalytic reforming of naphtha and separated from the aromatic mixture by distillation. From the mixed isomers, the ortho- can be obtained by distillation because its boiling point is sufficiently different. The meta- and para- are separated by either selective adsorption or by crystallization.

Producers ExxonMobil, Chevron Phillips, BP Amoco, Citgo, Koch, Hess,

Of the over 4 billion pounds of xylene made each year in the U.S., about40% is recovered as high-purity para-xylene, about 20% as ortho-xylene,and the rest used as mixed xylene in gasoline and for solvent purposes. Thereason for the large use in gasoline is because xylene (like benzene andtoluene) has very high fuel anti-knock characteristics (high octane rating).Thus, high-test gasoline has a higher percentage of aromatic hydrocarbonslike xylene than regular-grade.

Because ortho-xylene is more readily isolated and purified (by distilla-tion), it costs less than para-xylene. Like all petrochemicals, prices dependon the price of crude oil; but in early 2001, mixed-xylene was about 17cents/lb while para-xylene was only about 15 cents due to high manufac-turing capacity and low demand for use for making terephthalic acid. In theextremely high volumes in which such chemicals are sold, fractions of apenny difference in price can be very important.




XYLENE DERIVATIVES

PHTHALIC ANHYDRIDE (FROM O-XYLENE)

Uses A little over half of the phthalic anhydride produced is used for plasticizers in polymers while about 25% is used to manufacture unsaturated polyester resins. Phthalic anhydride also finds wide usage in the manufacture of paints (alkyd resins).

Manufacture

Suppliers Aristech Chemical, ExxonMobil, Koppers, Stepan, Sterling Chemical.

Plasticizers are very high-boiling liquids that when mixed with polymerslike poly(vinyl chloride) modify the properties of the polymer to produce amaterial with added flexibility without losing other desirable properties suchas strength. They are commonly made by reacting phthalic anhydride witha long-chain alcohol (typically eight carbons).

There are over 400 different commercial alkyd resin formulations basedon phthalic anhydride used in the coatings business. Alkyd resins for paintsare made by reacting phthalic anhydride with a poly-alcohol (usually fromnaturally occurring sources rather than synthetic) that contains unreacteddouble bonds. The paint dries by the resin crosslinking through reaction ofthe double bonds under the influence of oxygen in the air.

+ O2 (from air)

o-xylene phthalic anhydride

CH3

CH3

catalyst

CO

O

CO




XYLENE DERIVATIVES

TEREPHTHALIC ACID AND DIMETHYL TEREPHTHALATE

Uses Both terephthalic acid (TPA) and dimethyl terephthalate (DMT) are used exclusively for the manufacture of polyesters for textile fibers (e.g,. “Dacron”), films, soft-drink bottles, and engineering resins for automotive applications. The glycol used for most TPA-based polyesters is ethylene glycol. The polyester is then known as polyethylene terephthalate, or PET.

Manufacture

Suppliers BP Amoco, DuPont, Eastman Chemical, KoSa.

The manufacture of polyester fibers and films requires high-purity startingmaterials. Terephthalic acid is very difficult to purify because it cannot bedistilled and it is not soluble enough in any solvent for other types ofpurification. The dimethyl ester of terephthalic acid (DMT) can be distilled(although it is a high-melting solid) and so for many years the startingmaterial of choice to make polyester fibers was DMT. However, processeswere eventually developed that made very pure terephthalic acid directly sothat no purification was needed. Now, either starting material can be, and is,used for making polyesters.

+ O2 (from air)

p-xylene terephthalate acid dimethyl terephthalate

CH3

CH3

catalyst

COOH

COOH

CH3OH

COOCH3

COOCH3



149

Environmental Protection and Waste Disposal

Despite the fact that the chemical industry is absolutely essential to ourstandard of living, it has a poor image with the majority of people. It isblamed wholly or in part for many problems perceived to adversely affecthuman health and the environment. These public concerns include destruc-tion of the ozone layer, global warming, cancer-causing pollutants, endro-crine disruptors, poor air quality, poor water quality, etc. Because of theseperceptions, the chemical industry has become highly regulated by federal,state, and local laws.

7


150


ENVIRONMENTAL PROTECTION

What is the environment?It is all of the surrounding conditions and influences that affect thedevelopment of living things.

What is environmental pollution?It is any process, natural or man-made, that leads to harmful or objec-tionable changes to the environment.

What is environmental protection?It is any action taken to prevent environmental pollution.

The above questions and the answers may seem obvious to most people inview of the current and growing concern for our surroundings, but the termsare used so frequently in the press and on TV without explanation that itseems prudent to know the exact definitions.



151

TYPES OF POSSIBLE ENVIRONMENTAL POLLUTION BY THE CHEMICAL INDUSTRY

T

O

THE

A

IR

1.

Sulfur dioxide

: A toxic and corrosive gas emitted continuously indilute form, principally from the burning of fossil fuels.

2.

Toxic gas emissions

: Usually concentrated chlorine-containinggases or other harmful vapors released by accident.

3.

Foul-smelling gases

: Sulfur-containing gases such as hydrogen sul-fide that have an odor even at low concentrations.

4.

Dust

: Can be anywhere that minerals or finely-divided solids arehandled.

5.

Smoke

: Man-made smoke is now mainly controlled in developedcountries.

6.

Sprays

: Small liquid droplets in the air that can be caused byprocess upsets or by high wind.

7.

Radioactivity

: Accidental releases may occur.

T

O

W

ATER

1. S

ewage and organic industrial wastes

: This type of pollutionadversely affects the oxygen content of water (BOD, biologicaloxygen demand).

2.

Bacteria and viruses

: Usually from sewage.3.

Plant nutrients

: From sewage and drainage of fertilized farmland.Causes rapid algae growth that uses up oxygen (eutrophication).

4.

Organic pesticides

: Now mainly controlled by regulation.5.

Waste minerals and chemicals

: Caused by leaching of mineral andchemical waste heaps and landfills. Can cause enormous damage.

6.

Plant discharge into waterways

: Now strictly regulated by law.7.

Sediments

: Can cause turbidity and bottom sludge.8.

Heat

: Changes plant growth rate and amount of dissolved oxygen.


152


METHODS OF POLLUTION CONTROL

1.

Reduction of effluent volume

: A first step. May require a combina-tion of other control methods.

2.

Total elimination of effluent at the source

: The ultimate goal. Writ-ten into some regulations.

3.

Water reuse

: Widely practiced now.4.

Recovery and recycle of ingredients

: Better utilization of raw mate-rials saves money, natural resources, and the environment.

5.

Recovery of secondary products for sale

: Requires commitmentand ingenuity.

6.

Physical separations

: The method that is filling up the landfills.7.

Chemical treatment

: Widely practiced now. Will increase.8.

Biological treatment

: Used in all sewage plants and many settlingponds.

9.

Incineration

: The only practical method of disposal for somewastes. Has opposition from many environmental groups.

10.

Dilution

: A widely used method of control in the past. Now unac-ceptable under many regulations.



153

POLLUTION CONTROL LAWS AND REGULATIONS

In the U.S., there are local, state, and federal laws regulating health, safety,and the environment. The laws that address the area of pollution control alsocover health and safety, toxic substances, noise, transportation, and buildingsite approval.

N

ATIONAL

E

NVIRONMENTAL

P

OLICY

A

CT

, 1969 (NEPA)

This act requires that all federal agencies consider the environmental impactof their actions. These agencies must use all practicable means “to achievea harmonious balance between humanity and nature.”

O

CCUPATIONAL

S

AFETY

AND

H

EALTH

A

CT

, 1970 (OSHA)

Under this act, the Department of Labor sets safety standards, inspectsworkplaces, and sets penalties for violations. This act also established theNational Institute for Occupational Safety and Health (NIOSH) to developand establish health standards.

T

HE

R

ESOURCE

C

ONSERVATION

AND

R

ECOVERY

A

CT

, 1976 (RCRA)

This act governs in detail how the chemical industry must manage hazardouswastes. Generation, handling, transportation, and disposal are included inthe regulations.

T

OXIC

S

UBSTANCES

C

ONTROL

A

CT

, 1976 (TSCA)

Requires a federal inventory of existing chemicals in commerce, notificationfor listing of new chemicals or new uses for existing chemicals, and canrequire testing of chemicals for toxicity prior to approval for listing.

T

HE

C

LEAN

A

IR

A

CT

, 1970

AND

S

UBSEQUENT

A

MENDMENTS

Gives the Environmental Protection Agency (EPA) power to adopt andenforce air pollution standards.


154


PARTIAL HISTORY OF POLLUTIONAND POLLUTION CONTROLBY THE CHEMICAL INDUSTRY

Year

ca. 2500

BC

The Sumerians used sulfur compounds for insect control.

ca.1500

BC

The Chinese used naturally occurring chemicals to control insects in grain.

>

1700 Copper pollution in Palestine due to copper smelting thousands of years before.

1773 Discharge of hydrogen chloride into the air from the manufacture of soda ash. Continued until 1864 when early pollution control laws were passed.

>

1900 Sulfuric acid manufacture released both sulfur oxides and arsenic into the environment.

1906 The Pure Food and Drug Act established the Food and Drug Administration (FDA).

1917 Workers making explosives for World War I developed jaundice from dust inhalation.

1921 A chemical nitrate plant in Germany exploded, killing more than 600 people.

1935 The Chemical Manufacturers Association (CMA), a trade group, established a Water Resources Committee to study the effect of their industry on water bodies.

1947 A ship in Texas City, TX, loaded with ammonium nitrate exploded, killing 462 people and injuring more than 3000.

1948 The CMA established an Air Quality Committee to study methods for improving air quality.

1958 The Delaney Amendment to the Food and Drug Act addressed the control of food additives.

1959 Cranberries destroyed by the federal government due to contamination by a weedkiller.

1960 A drug prescribed in the 1950s to prevent miscarriages was reported to cause cancer and other problems in female children of the drug recipients.



155

1962 A drug prescribed as a tranquilizer for pregnant women caused severe birth defects.

1962 A book indicted DDT and other pesticides for the poisoning of wildlife. DDT was banned in the U.S. in 1972, but it remains in use in developing countries.

1965 Nonbiodegradable detergents were banned when they were found as contaminants in some rivers.

1965 In Japan, 46 people died from eating mercury-contaminated fish from a body of water polluted by a plastics company.

1966 Polychlorinated biphenyls (PCBs), a carcinogen in animals, were found in the environment. The use of PCBs was banned in 1978.

1969 A new artificial sweetener (cyclamate) was banned because it caused cancer in animals when fed in large amounts. Not banned in other countries.

1970 Occupational Safety and Health Act (OSHA) set safety standards for workplaces.

1974 An explosion at a nylon-intermediates plant in England killed28 people.

1974 Three men working at a poly(vinyl chloride) plant were found to have a rare form of cancer.

1975 Almost half of the workers at a pesticide plant in Virginia were found to be suffering from poisoning. The nearby James River containing oyster beds was found to be contaminated with the same chemical.

1976 A chemical plant in Italy exploded and spread a known animal carcinogen (dioxin) over a large area. No deaths or birth defects were ever shown to be due to this release.

1976 The Toxic Substances Control Act (TSCA) was adopted.

1976 The Resource Conservation and Recovery Act (RCRA) waspassed.

1977 Polyacrylonitrile plastic beverage bottles were banned because of possible migration of acrylonitrile (a weak carcinagen) into the bottle contents.

1977 Some employees making a soil fumigant (DBCP) became sterile. It is now banned.

1977 Benzene was linked to high rates of leukemia.


156


1977 A fire-retardant (Tris) used to treat children’s sleepwear was found to be an animal carcinogen.Tris is now banned.

1978 Chlorofluorocarbons banned as aerosol propellants because of potential stratospheric ozone destruction.

1978 An old chemical dump in New York (Love Canal) started to leak into the environment.

1980 Regulation of asbestos insulation in school buildings initiated.

1980 The Comprehensive Environmental Response, Compensation and Liability Act established a “Superfund” to cleanup hazardous landfills.

1983 Over 600 people in Spain died as a result of using contaminated oil sold as “olive oil.”

1984 In Bhopal, India, more than 2500 people died from a release of methyl isocyanate.

1985 The chemical industry initiated the “Responsible Care” program to improve the public’s perception of the industry. This program promotes environmental, health, and safety performance and total honesty in dealing with the press and the public. Now embraced and practiced by virtually all chemical companies.

1997 According to the U.S. Bureau of Labor Statistics, the lost workday injuries (per 100 employees per year) for the chemical industry was 2.1. The corresponding number for all manufacturing was 4.2. The numbers for other occupations were: agriculture 4.0, mining 3.7, construction 4.4, transportation 4.7, and wholesale and retail trade 2.9.


157

Information Sources

Sources for information on chemistry and the chemical industry are listed. The typeof information available (see keywords) in each source is indicated by the capitalletters in parentheses following each listing.

Of these sources,

Kirk-Othmer’s Encyclopedia of Chemical Technology

is par-ticularly recommended for questions on chemistry and on end uses. For informationon properties and on toxicity and handling hazards,

Patty’s Industrial Hygiene

,Material Safety Data Sheets (MSDS), and the Aldrich catalog are very useful.Questions on industrial chemistry should be directed to

Ullman’s Encyclopedia ofIndustrial Chemistry

, and the texts by Chenier, Heaton, and White.

Hawley’s Con-densed Chemical Dictionary

is valuable as a source for definitions of the terms(language) of chemistry.

TX544_Frame_Information.fm Page 157 Tuesday, December 4, 2001 2:27 PM


158


INFORMATION SOURCES

A. Industrial Chemistry F. NomenclatureB. Organic Chemistry G. EnvironmentalC. Inorganic Chemistry H. Toxicity and Handling HazardsD. Polymer Chemistry I. Facts and FigureE. Properties J. End Uses

1. Aldrich Chemical Co.,

Catalog Handbook of Fine Chemicals,

current edition,Aldrich Chemical Co., 1001 West Saint Paul Ave., Milwaukee, WI 53233.(E,F,G,H)

2. Arpe, H.J. (Ed.),

Ullman’s Encyclopedia of Industrial Chemistry,

5th ed., 37vols., VCH Publishers, 1997. (A,B,C,D,E,G,I,J)

3. Budavars, S. (Ed.),

The Merck Index,

12th ed., Merck & Co., 1996. (E,F,H,J)4. Burdick, D.L. and Leffler, W.L.,

Petrochemicals in Nontechnical Language,

John Wiley & Sons, 1986. (A,B,C,D,I,J)5. Chenier, P.J.,

Survey of Industrial Chemistry,

2nd ed., VCH Publishers, 1992.(A,B,C,D,I)

6. Harris, R. (Ed.),

Patty’s Industrial Hygiene,

5th ed., 4 vols., John Wiley &Sons, 2000. (E,F,G,H,J)

7. Heaton, C.J. (Ed.),

An Introduction to Industrial Chemistry,

Blackie & Son,Ltd., 1991. (A,B,C,D,I,J)

8. Kroschwitz, J.I. et al. (Ed.),

Kirk-Othmer’s Encyclopedia of Chemical Tech-nology,

4th ed., 27 vols., Wiley-Interscience, 1991–1998. (A,B,C,D,E,J)9. Kroschwitz, J.I. et al. (Ed.),

Kirk-Othmer’s Concise Encyclopedia of Chem-ical Technology,

4th ed., Wiley-Interscience, 1999. (A,B,C,D,E,J)10. Lewis, R.J. (Ed.),

Hawley’s Condensed Chemical Dictionary,

13th ed., JohnWiley & Sons, 1997. (E,F,H,J)

11. Lide, D.R. (Ed.),

Handbook of Chemistry and Physics,

81st ed., CRC Press,2000. (B,C,E,F,H,I)

12. Material Safety Data Sheets (MSDS) — Available from the chemical man-ufacturer and the marketing agent. Also available online at MSDS-SEARCH.com and at Sigma-Aldrich.com. (E,F,G,H)

13. White, H.L.,

Introduction to Industrial Chemistry,

John Wiley & Sons, 1986.(A,B,C,D,I,J)

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Chemistry and the Chemical Industry a Practical Guide for Non-Chemists

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